Java DB Server and Administration Guide
Version 10.6
Derby Document build:
September 27, 2010, 11:12:06 AM (EDT)
Version 10.6 Java DB Server and Administration Guide
Contents
Copyright •
License •
Relationship between Java DB and Derby •
About this guide •
Purpose of this guide •
Audience •
How this guide is organized •
Part one: Derby Server Guide •
Derby in a multi-user environment •
Derby in a server framework •
About this guide and the Network Server documentation •
Using the Network Server with preexisting Derby applications •
The Network Server and JVMs •
Installing required jar files and adding them to the classpath •
Starting the Network Server •
Shutting down the Network Server •
Obtaining system information •
Accessing the Network Server by using the network client driver •
Accessing the Network Server by using a DataSource object •
XA and the Network Server •
Using the Derby tools with the Network Server •
Differences between running Derby in embedded mode and using the Network Server •
Setting port numbers •
Managing the Derby Network Server •
Overview •
Setting Network Server properties •
Verifying Startup •
Managing the Derby Network Server remotely by using the servlet interface •
Start-up page •
Running page •
Trace session page •
Trace directory page •
Set Network Server parameters •
Derby Network Server advanced topics •
Network Server security •
Running the Network Server under the security manager •
Running the Network Server with User Authentication •
Network encryption and authentication with SSL/TLS •
Configuring the Network Server to handle connections •
Controlling logging by using the log file •
Controlling tracing by using the trace facility •
Derby Network Server sample programs •
The NsSample sample program •
Network Server sample programs for embedded and client connections •
Part two: Derby Administration Guide •
Checking database consistency •
The SYSCS_CHECK_TABLE function •
Sample SYSCS_CHECK_TABLE error messages •
Sample SYSCS_CHECK_TABLE queries •
Backing up and restoring databases •
Backing up a database •
Restoring a database from a backup copy •
Creating a database from a backup copy •
Roll-forward recovery •
Replicating databases •
Starting and running replication •
Stopping replication •
Forcing a failover •
Replication and security •
Replication failure handling •
Logging on a separate device •
Using the logDevice=logDirectoryPath attribute •
Example of creating a log in a non-default location •
Example of moving a log manually •
Issues for logging in a non-default location •
Obtaining locking information •
Monitoring deadlocks •
Reclaiming unused space •
Trademarks •
•
Java DB Server and Administration Guide
Apache Software FoundationJava DB Server and Administration GuideApache Derby
Copyright
Copyright 2004-2010 The Apache Software Foundation
Copyright 2010 Oracle and/or its affiliates. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.
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Relationship between Java DB and Derby
Java DB is a relational database management system that is based on the Java programming language and SQL. Java DB is a commercial release of the Apache Software Foundation's (ASF) open source relational database project. The Apache project is called Derby.
The Java DB product includes Derby without any modification whatsoever to the underlying source code.
Java DB technical support is available for purchase through the Java For Business product at Oracle.
Because Java DB and Derby have the same functionality, the Java DB documentation refers to the core functionality as Derby.
Java DB Version 10.6 is based on the Version 10.6 release of Derby. References to "Derby" in the Java DB documentation refer to the Version 10.6 release of Apache Derby.
About this guide
This section describes who this guide is for as well as how to use it.
Purpose of this guide
This guide explains how to use Derby in a multiple-client environment. It also provides information that a server administrator might need to keep Derby running with a high level of performance and reliability in a server framework or in a multiple-client application server environment (When running in embedded mode, Derby databases typically do not need any administration).
To connect multiple clients with Derby, you can embed Derby in a server framework that you choose, or you can use the Derby Network Server. This guide describes these options.
Audience
The first part of this guide is intended for developers of client/server and multiple-client applications. The second part of this guide is intended for administrators.
How this guide is organized
This guide includes the following two parts:
Part one: Derby Server Guide

• |  | Derby in a multi-user environment Describes the different options for embedding Derby in a server framework and explains the Network Server option.
• |  | Using the Network Server with preexisting Derby applications Describes how to change existing Derby applications to work with the Network Server.
• |  | Managing the Derby Network Server Describes how to use shell scripts, the command line, and the Network Server API to manage the Network Server.
• |  | Managing the Derby Network Server remotely by using the servlet interface Describes how to use the servlet interface to manage the Network Server.
• |  | Derby Network Server advanced topics Describes advanced topics for Derby Network Server users.

Part two: Derby Administration Guide

• |  | Checking database consistency Describes how to check the consistency of Derby databases.
• |  | Backing up and restoring databases Describes how to back up a database when it is online.
• |  | Logging on a separate device Describes how to put a database's log on a separate device, which can improve the performance of large databases.
• |  | Obtaining locking information Describes how to get detailed information about locking status.
• |  | Reclaiming unused space Describes how to identify and reclaim unused space in tables and related indexes.

Part one: Derby Server Guide
This part of the guide explains the Derby Network Server and other server frameworks.
Derby in a multi-user environment
This section describes how to use Derby in a multi-user (or "server") environment.
Derby in a server framework
In a sense, Derby is always an embedded product. You can embed it in an application in which users access the database from a single JVM or you can embed it in a server framework (an application that allows users from different JVMs to connect to Derby simultaneously). When Derby is embedded in an application, the local JDBC driver calls the local Derby database. When Derby is embedded in a server framework, the server framework's connectivity software provides data to multiple client JDBC applications over a network or the Internet.
For local or remote multi-user connectivity (multiple users who access Derby from different JVMs), use the Derby Network Server. If you require features that are not included in the Network Server, you can embed the basic Derby product in another server framework.
Connectivity configurations
There are several ways to embed Derby in a server framework:
Use the Network Server
This is the easiest way to provide connectivity to multiple users who are accessing Derby databases from different JVMs. The Derby Network Server provides this kind of connectivity to Derby databases within a single system or over a network.
Purchase another server framework
You can use Derby within many server frameworks, such as IBM WebSphere Application Server.
Write your own framework
Derby's flexibility allows other configurations as well. For example, rather than embedding Derby in a server that communicates with a client that uses JDBC, you can embed Derby within a servlet in a web server that communicates with a browser using HTTP.
Multiple-client features available in Derby
Derby contains some features that are useful for developing multi-user applications.
Row-level locking:
To support multi-user access, Derby utilizes row-level locking. However, you can configure Derby to use table-level locking in environments that have few concurrent transactions (for example, a read-only database) . Table-level locking is preferable if there are few or no writes to the server, while row-level locking is essential for good performance if many clients write to the server concurrently. The Derby optimizer tunes lock choice for queries automatically.
Multiple concurrency levels:
Derby supports SERIALIZABLE (RR), REPEATABLE (RS), READ COMMITTED (CS), and READ UNCOMMITTED (UR) isolation levels.
CS
CS (the default isolation level) provides the best balance between concurrency and consistency in multiple-client environments.
RS
RS provides less consistency than RR but allows more concurrency.
RR
RR provides greatest consistency.
UR
UR provides maximum concurrency, if uncommitted values are allowed in the query. It is typically used if approximate results are acceptable.
See "Types and Scope of Locks in Derby Systems" in the Java DB Developer's Guide for more information.
Multi-connection and multi-threading:
Derby allows multiple simultaneous connections to a database, even in embedded mode. Derby is also fully multi-threaded, and you can have multiple threads active at the same time. However, JDBC semantics impose some limitations on multi-threading. See the Java DB Developer's Guide for more information.
Administrative tools:
Derby provides some tools and features to assist database administrators, including:

• |  | Consistency checker
• |  | Online backup
• |  | The ability to put a database's log on a separate device

These tools and features are discussed in part two of this guide. See the sections in that part for more information.
The Derby Network Server
The Derby Network Server provides multi-user connectivity to Derby databases within a single system or over a network. The Network Server uses the standard Distributed Relational Database Architecture (DRDA) protocol to receive and reply to queries from clients. Databases are accessed through the Derby Network Server by using the Derby Network Client driver.
The Network Server is a solution for multiple JVMs that connect to the database, unlike the embedded scenario where only one JVM runs as part of the system. When Derby is embedded in a single-JVM application, the embedded JDBC driver calls the local Derby database. When Derby is embedded in a server framework, the server framework's connectivity software provides data to multiple client JDBC applications over a network or the Internet.
To run the Derby Network Server, you need to install the following files:

• |  | On the server side, install derby.jar and derbynet.jar.
• |  | On the client side, install derbyclient.jar.

There are several ways to manage the Derby Network Server, including:

• |  | Through the command line
• |  | By using .bat and .ksh scripts
• |  | Through the servlet interface
• |  | With your own Java program (written using the Network Server API)
• |  | By setting Network Server properties

Using the Network Server with preexisting Derby applications explains how to change existing Java applications that currently run against Derby in embedded mode to run against the Derby Network Server.
Managing the Derby Network Server explains how to manage the Network Server by using the command line, including starting and stopping it.
Managing the Derby Network Server remotely by using the servlet interface explains how to use the servlet interface to manage the Network Server.
Derby Network Server advanced topics contains advanced topics for Derby Network Server users.
Because of the differences in JDBC drivers that are used, you might encounter differences in functionality when running Derby in the Network Server framework as opposed to running it embedded in a user application. Refer to Using the Network Server with preexisting Derby applications for a complete list of the differences between embedded and Network Server configurations.
Embedded servers
Because Derby is written in Java, you have great flexibility in how you choose to configure your deployment. For example, you can run Derby, the JDBC server framework, and another application in the same JVM as a single process.
How to start an embedded server from an application
In one thread, the embedding application starts the local JDBC driver for its own access.

    /*
        If you are running on JDK 6 or higher, you do not
        need to invoke Class.forName(). In that environment, the
        EmbeddedDriver loads automatically.
    */
    Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
    Connection conn = DriverManager.getConnection(
        "jdbc:derby:sample");

In another thread, the same application starts the server framework to allow remote access. Starting the server framework from within the application allows both the server and the application to run in the same JVM.
Embedded server example
You can start the Network Server in another thread automatically when Derby starts by setting the derby.drda.startNetworkServer property (see Setting Network Server properties), or you can start it by using a program. The following example shows how to start the Network Server by using a program:

    import org.apache.derby.drda.NetworkServerControl;
    import java.net.InetAddress;
    NetworkServerControl server = new NetworkServerControl
    	(InetAddress.getByName("localhost"),1527);
    server.start(null);

The program that starts the Network Server can access the database by using either the embedded driver or the Network Client driver. The server framework's attempt to boot the local JDBC driver is ignored because it has already been booted within the application's JVM. The server framework simply accesses the instance of Derby that is already booted. There is no conflict between the application and the server framework.
The remote client can then connect through the Derby client driver:

    String nsURL="jdbc:derby://localhost:1527/sample";
    java.util.Properties props = new java.util.Properties();
    props.setProperty("user","usr");
    props.setProperty("password","pwd");

    /*
        If you are running on JDK 6 or higher, you do not
        need to invoke Class.forName(). In that environment, the
        ClientDriver loads automatically.
    */
    Class.forName("org.apache.derby.jdbc.ClientDriver");
    Connection conn = DriverManager.getConnection(nsURL, props);

    /*interact with Derby*/
    Statement s = conn.createStatement();

    ResultSet rs = s.executeQuery(
    "SELECT * FROM HotelBookings");

About this guide and the Network Server documentation
This guide assumes that you are familiar with Derby features and tuning. Before reading this guide, you should first learn about basic Derby functionality by reading the Java DB Developer's Guide. Also, because multi-user environments typically have performance and tuning issues, you should read Tuning Java DB.
Using the Network Server with preexisting Derby applications
You must modify Java applications that currently run against Derby in embedded mode so that they work with the Derby Network Server. The topics in this section discuss these changes.
The Network Server and JVMs
The Derby Network Server is compatible with Java Platform, Standard Edition, v 1.4.2 (J2SE) and above.
Installing required jar files and adding them to the classpath
To use the Network Server and network client driver, add the following jar file to your server classpath:

• |  | derbyrun.jar

Adding this file to your classpath has the effect of including all of the Derby classes in your classpath. These classes are in the following jar files, which you can also add to your classpath separately:

• |  | derbynet.jar This jar file contains the Network Server code. It must be in your classpath to start the Network Server.
• |  | derby.jar This jar file contains the Derby database engine code. It must be in the classpath in order for the Network Server to access Derby databases. derby.jar is included in the Class-Path attribute of derbynet.jar's manifest file. If you have derbynet.jar in the classpath and derby.jar is in the same directory as derbynet.jar, it is not necessary to include derby.jar explicitly.
• |  | derbyclient.jar This jar file contains the Derby Network Client JDBC driver that is necessary for communication with the Network Server. It must be in the classpath of the application on the client side in order to access Derby databases over a network.

All of the jar files are in the $DERBY_HOME/lib directory.
Derby provides script files for setting the classpath to work with the Network Server. The scripts are located in the $DERBY_HOME/bin directory.

• |  | setNetworkClientCP.bat (Windows)
• |  | setNetworkClientCP (UNIX)
• |  | setNetworkServerCP.bat (Windows)
• |  | setNetworkServerCP (UNIX)

See Managing the Derby Network Server and Getting Started with Java DB for more information on setting the classpath.
Starting the Network Server
To start the Network Server, you can invoke a script, a jar file, or a class.
> Important: Note that you should always properly shut down the Network Server after use, because failure to do so might result in unpredictable side-effects, such as blocked ports on the server.
You are strongly urged to enable user authentication when you run a Network Server. For details on how to configure user authentication, please consult the "Working with user authentication" section in the Developer's Guide. You are also urged to install a Java security manager with a customized security policy. For details on how to do this, see Customizing the Network Server's security policy.
You can start the Network Server in any of the following ways:

• |  | If you are relatively new to the Java programming language, follow the instructions in "Setting up your environment" in Getting Started with Java DB to set the DERBY_HOME and JAVA_HOME environment variables and to add DERBY_HOME/bin to your path. Then use the startNetworkServer.bat script to start the Network Server on Windows machines and the startNetworkServer script to start the Network Server on UNIX systems. These scripts are located in $DERBY_HOME/bin, where $DERBY_HOME is the directory where you installed Derby. You can run NetworkServerControl commands only from the host that started the Network Server.
Operating System | Command
Windows |
    set DERBY_HOME=C:\derby
    set JAVA_HOME=C:\Program Files\Java\jdk1.5.0_10
    set PATH=%DERBY_HOME%\bin;%PATH%
    startNetworkServer
UNIX (Korn Shell) |
    export DERBY_HOME=/opt/derby
    export JAVA_HOME=/usr/j2se
    export PATH="$DERBY_HOME/bin:$PATH"
    startNetworkServer
• |  | If you are a regular Java user but are new to Derby, set the DERBY_HOME environment variable, then use a java command to invoke the derbyrun.jar or derbynet.jar file:
Operating System | Command
Windows |
    set DERBY_HOME=C:\derby
    java -jar %DERBY_HOME%\lib\derbyrun.jar server start
    or
    java -jar %DERBY_HOME%\lib\derbynet.jar start
UNIX (Korn Shell) |
    export DERBY_HOME=/opt/derby
    java -jar $DERBY_HOME/lib/derbyrun.jar server start
    or
    java -jar $DERBY_HOME/lib/derbynet.jar start
To see the command syntax, invoke derbyrun.jar server or derbynet.jar with no arguments.
• |  | If you are familiar with both the Java programming language and Derby, you have already set DERBY_HOME. Set your classpath to include the Derby jar files. Then use a java command to invoke the NetworkServerControl class directly.
Operating System | Command
Windows |
    %DERBY_HOME%\bin\setNetworkServerCP
    java org.apache.derby.drda.NetworkServerControl start
UNIX (Korn Shell) |
    $DERBY_HOME/bin/setNetworkServerCP
    java org.apache.derby.drda.NetworkServerControl start

The default system directory is the directory in which Derby was started. (See the Java DB Developer's Guide for more information about the default system directory.)
You can specify a different host or port number when you start the Network Server by specifying an option to the command.

• |  | Specify a port number other than the default (1527) by using the -p portnumber option, as shown in the following example:
    java org.apache.derby.drda.NetworkServerControl start -p 1368
• |  | Specify a specific interface (host name or IP address) to listen on other than the default (localhost) by using the -h option, as shown in the following example:
    $DERBY_HOME/bin/startNetworkServer -h myhost -p 1368
where myhost is the host name or IP address. Remember: Before using the -h option, you should run under the Java security manager with a customized security policy and you should enable user authentication.

By default, the Network Server will listen to requests only on the loopback address, which means that it will only accept connections from the local host.
Starting the Network Server from a Java application
Note that you should always properly shut down the Network Server after use, because failure to do so might result in unpredictable side-effects, such as blocked ports on the server.
There are two ways to start the Network Server from a Java application.

• |  | You can include the following line in the derby.properties file:
    derby.drda.startNetworkServer=true
This starts the server on the default port, 1527, listening on localhost (all interfaces). To specify a different port or a specific interface in the derby.properties file, include the following lines, respectively:
    derby.drda.portNumber=1110
    derby.drda.host=myhost
You can also specify the startNetworkServer and portNumber properties by using a Java command:
    java -Dderby.drda.startNetworkServer=true
    -Dderby.drda.portNumber=1110
    -Dderby.drda.host=myhost yourApp
• |  | You can use the NetworkServerControl API to start the Network Server from a separate thread within a Java application:
    NetworkServerControl server = new NetworkServerControl();
    server.start (null);

Starting the Network Server on IPv6/Ipv4 dual stack Windows machines
The following JVM properties need to be added to the command when starting the server on IPv6/Ipv4 dual stack Windows machines:

    -Djava.net.preferIPv4Stack=false
    -Djava.net.preferIPv6Addresses=true

Shutting down the Network Server
To shut down a Network Server, you can invoke a script, a jar file, or a class.
The scripts to shut down a Network Server are located in the $DERBY_HOME/bin directory.
> Important: If user authentication is enabled, you must specify a valid Derby user name and password; if the user authentication check fails, you'll see an authentication error and the running server remains intact. Note that Derby does not yet restrict the shutdown privilege to specific users: the server can be shut down by any user on the server machine who presents valid credentials.

• |  | To shut down the Network Server by using the scripts provided for Windows systems, use:
    stopNetworkServer.bat [-h hostname] [-p portnumber] [-user username] [-password password]
• |  | To shut down the Network Server by using the scripts provided for UNIX systems, use:
    stopNetworkServer [-h hostname] [-p portnumber] [-user username] [-password password]

Shutting down by using the command line
From the command line, you can shut down a Network Server by invoking a jar file or a class.
Note that you need to provide user credential arguments to shut down a server running with user authentication.

• |  | To shut down the Network Server by invoking a jar file from the $DERBY_HOME/lib directory, use:
    java -jar derbyrun.jar server shutdown [-h <hostname>] [-p <portnumber>] [-user <username>] [-password <password>]
or
    java -jar derbynet.jar shutdown [-h <hostname>] [-p <portnumber>] [-user <username>] [-password <password>]
• |  | To shut down the Network Server by invoking a class, use:
    java org.apache.derby.drda.NetworkServerControl shutdown [-h <hostname>] [-p <portnumber>] [-user <username>] [-password <password>]

Shutting down by using the API
You can use the NetworkServerControl API to shut down the Network Server from within a Java application. The name of the method that you use to shutdown the Network Server is shutdown().
For example, the following command shuts down the Network Server running on the current machine using the default port number (1527):

    NetworkServerControl server = new NetworkServerControl();
    server.shutdown();

To shut down a server running with user authentication, you need to use a NetworkServerControl instance created with user credentials:

    NetworkServerControl server = new NetworkServerControl(username, password);
    server.shutdown();

Obtaining system information
You can obtain information about the Network Server, such as version and current property values, Java information, and Derby database server information, by using the sysinfo utility. The sysinfo utility is available from scripts, the command line, the NetworkServerControl API, and through the servlet interface.
The following scripts are located in the $DERBY_HOME/bin directory. Before running these scripts, make sure that the Derby Network Server is started.

• |  | Run the following script to obtain information about the Network Server on a Windows system:
    NetworkServerControl.bat sysinfo [-h hostname][-p portnumber]
• |  | Run the following script to obtain information about the Network Server on a UNIX system:
    NetworkServerControl sysinfo [-h hostname] [-p portnumber]

For more information on the sysinfo utility, see the Java DB Tools and Utilities Guide.
You can also use Java Management Extensions (JMX) technology to obtain system information. For details, visit the wiki page http://wiki.apache.org/db-derby/DerbyJMX and refer to the API documentation for the packages org.apache.derby.mbeans and org.apache.derby.mbeans.drda. For information on JMX technology, see http://java.sun.com/javase/technologies/core/mntr-mgmt/javamanagement/.
Obtaining system information by using the command line
To run sysinfo from the command line, use a command like one of the following while the Network Server is running:

    java -jar $DERBY_HOME/lib/derbyrun.jar server sysinfo
      [-h hostname][-p portnumber]

    java org.apache.derby.drda.NetworkServerControl sysinfo
      [-h hostname][-p portnumber]

Administrative commands such as sysinfo can only execute on the host where the server was started, even if the server was started with the -h option.
Obtaining system information by using the API
The sysinfo method produces the same information as the sysinfo command. The signature for this method is

    String getSysinfo();

For example:

    NetworkServerControl serverControl = new NetworkServerControl();
    String myinfo = serverControl.getSysinfo();

The getSysinfo() method returns information about the Network Server that is running on the current machine on the default port number (1527).
Obtaining Network Server runtime information:
Use the runtimeinfo command or getRuntimeInfo method to get memory usage and current session information about the Network Server including user, database, and prepared statement information.

• |  | To run runtimeinfo from the command line:
    java org.apache.derby.drda.NetworkServerControl runtimeinfo
       [-h <hostname>][<-p portnumber>]
• |  | The getRuntimeInfo method returns the same information as the runtimeinfo command. The signature for the getRuntimeInfo method is String getRuntimeInfo(). For example:
    NetworkServerControl serverControl = new NetworkServerControl();
    String myinfo = serverControl.getRuntimeInfo();

Obtaining Network Server properties by using the getCurrent Properties method:
The getCurrentProperties method is a Java method that you can use to obtain information about the Network Server. It returns a Properties object with the value of all the Network Server properties as they are currently set.
The signature of this method is:

    Properties getCurrentProperties();

For example:

    NetworkServerControl server = new NetworkServerControl();
    Properties p = server.getCurrentProperties();
    p.list(System.out);
    System.out.println(p.getProperty("derby.drda.host"));

As shown in the previous example, you can look up the current properties and then work with individual properties if needed by using various APIs on the Properties class. You can also print out all the properties by using the Properties.list() method.
See Managing the Derby Network Server remotely by using the servlet interface for information about obtaining system information using the servlet interface.
Accessing the Network Server by using the network client driver
When connecting to the Network Server, your application needs to load a driver and connection URL that is specific to the Network Server. In addition, you must specify a user name and password if you are using authentication.
The driver that you need to access the Network Server is:

    org.apache.derby.jdbc.ClientDriver

The syntax of the URL that is required to access the Network Server is:

    jdbc:derby://<server>[:<port>]/
    <databaseName>[;<URL attribute>=<value> [;...]]

where the <URL attribute> is either a Derby embedded or network client attribute.
To access an in-memory database using the Network Server, the syntax is:

    jdbc:derby://<server>[:<port>]/memory:
    <databaseName>[;<URL attribute>=<value> [;...]]

For more information, see "Using in-memory databases" in the Java DB Developer's Guide.
For both driver and DataSource access, the database name (including path), user, password and other attribute values must consist of single-byte characters that can be converted to EBCDIC. The total byte length of the database name plus attributes when converted to EBCDIC must not exceed 255 bytes. You may be able to work around this restriction for long paths or paths that include multibyte characters by setting the derby.system.home system property when starting Network Server and accessing the database with a relative path that is shorter and does not include multibyte characters.
Table 1. Standard JDBC DataSource properties

Property | Type | Description | URL attribute | Notes
databaseName | String | The name of the database. This property is required. | ' | This property is also available using EmbeddedDataSource.
dataSourceName | String | The data source name. | ' | This property is also available using EmbeddedDataSource.
description | String | A description of the data source. | ' | This property is also available using EmbeddedDataSource.
user | String | The user's account name. | user | Default is APP. This property is also available using EmbeddedDataSource.
password | String | The user's database password. | password | This property is also available using EmbeddedDataSource.
serverName | String | The host name or TCP/IP address where the server is listening for requests. | ' | Default is "localhost".
portNumber | Integer | The port number where the server is listening for requests. | ' | Default is "1527".

Table 2. Client-specific DataSource properties

Property | Type | Description | URL attribute | Notes
traceFile | String | The filename for tracing output. Setting this property turns on tracing. See Network client tracing. | traceFile | '
traceDirectory | String | The directory for the tracing output. Each connection will send output to a separate file. Setting this property turns on tracing. See Network client tracing. | traceDirectory | '
traceLevel | Integer | The level of client tracing if traceFile or traceDirectory are set. | traceLevel | The default is TRACE_ALL.
traceFileAppend | Boolean | Value is true if tracing output should append to the existing trace file. | traceFileAppend | The default is false.
securityMechanism | Integer | The security mechanism. See Network client security. | securityMechanism | The default is USER_ONLY _SECURITY.
retrieveMessageText | Boolean | Retrieve message text from the server. A stored procedure is called to retrieve the message text with each SQLException and might start a new unit of work. Set this property to false if you do not want the performance impact or when starting new units of work. | retrieveMessageText | The default is true.
ssl | String | The SSL mode for the client connection. See Network encryption and authentication with SSL/TLS | ssl | The default is off.

Table 3. Server-Specific DataSource properties

Property | Type | Description | URL attributes | Notes
connectionAttributes | String | Set to the list of Derby embedded connection attributes separated by semicolons. | Various | This property is also available using EmbeddedDataSource. See the Java DB Reference Manual for more information about the various connection attributes.
createDatabase | String | If set to "create", create the database specified with databaseName property. | create | This property is also available using EmbeddedDataSource. See the Java DB Reference Manual for more information. Similar to setting connectionAttribute to "create=true". Only "create" is allowed, other values equate to null. The result of conflicting settings of createDatabase, shutdownDatabase and connectionAttributes is undefined.
shutdownDatabase | String | If set to "shutdown", shutdown the database specified with databaseName property. | shutdown | This property is also available using EmbeddedDataSource. See the Java DB Reference Manual for more information. Similar to setting connectionAttribute to "shutdown=true". Only "shutdown" is allowed, other values equate to null. The result of conflicting settings of createDatabase, shutdownDatabase and connectionAttributes is undefined. If authentication and sqlAuthorization are both enabled, database shutdown is restricted to the database owner.

Note that setAttributesAsPassword , which is available for the embedded DataSource, is not available for the client DataSource.
Network client security
The Derby Network Client allows you to select a security mechanism by specifying a value for the securityMechanism property.
You can set the securityMechanism property in one of the following ways:

• |  | When you are using the DriverManager interface, set securityMechanism in a java.util.Properties object before you invoke the form of the getConnection method, which includes the java.util.Properties parameter.
• |  | When you are using the DataSource interface to create and deploy your own DataSource objects, invoke the DataSource.setSecurityMechanism method after you create a DataSource object.

Security mechanisms supported by the Derby Network Client lists the security mechanisms that the Derby Network Client supports, and the corresponding property value to specify to obtain this securityMechanism. The default security mechanism is the user id only if no password is set. If the password is set, the default security mechanism is both the user id and password. The default user is APP if no other user is specified.
Table 4. Security mechanisms supported by the Derby Network Client

Security mechanism | securityMechanism property value | Comments
User id and password | ClientDataSource.CLEAR_TEXT_PASSWORD_SECURITY (0x03) | Default if password is set
User id only | ClientDataSource.USER_ONLY_SECURITY (0x04) | Default if password is not set
Strong password substitution | ClientDataSource.STRONG_PASSWORD_SUBSTITUTE_SECURITY (0x08) | Strong password substitution can be used only with Derby's BUILTIN authentication mechanism or with authentication disabled. Also, for the BUILTIN mechanism, strong password substitution does not work for database-level users whose password has been protected by a custom message digest algorithm specified by the derby.authentication.builtin.algorithm property.
Encrypted user id and encrypted password | ClientDataSource.ENCRYPTED_USER_AND_PASSWORD_SECURITY (0x09) | Encryption requires a JCE implementation that supports the Diffie-Hellman algorithm with a public prime of 256 bits.

Network client tracing
The Derby Network client provides a tracing facility to collect JDBC trace information and view protocol flows.
There are various ways to obtain trace output. However, the easiest way to obtain trace output is to use the traceFile=path attribute on the URL in ij. The following example shows all tracing going to the file trace.out from an ij session.

    ij>connect 'jdbc:derby://localhost:1527/mydb;
    create=true;traceFile=trace.out;user=user1;password=secret4me';

To append trace information to the specified file, use the traceFileAppend=true URL attribute in addition to traceFile=path.
For more information, see "traceFile=path attribute" and "traceFileAppend=true attribute" in the Java DB Reference Manual.
Implementing ClientDataSource tracing
You can use one of three methods to collect tracing data while obtaining connections from the ClientDataSource:

• |  | Use the setLogWriter(java.io.PrintWriter) method of ClientDataSource and set the PrintWriter to a non-null value.
• |  | Use the setTraceFile(String filename) method of ClientDataSource.
• |  | Use the setTraceDirectory(String dirname) method of ClientDataSource to trace each connection flow in its own file for programs that have multiple connections.

Implementing DriverManager tracing
Use one of the following two options to enable and collect tracing information while obtaining connections using the DriverManager:

• |  | Use the setLogWriter(java.io.PrintWriter) method of DriverManager and set the PrintWriter to a non null-value.
• |  | Use the traceFile=path or traceDirectory=path URL attributes to set these properties prior to creating the connection with the DriverManager.getConnection() method. For more information, see "traceFile=path attribute" and "traceDirectory=path attribute" in the Java DB Reference Manual.

Changing the default trace level
The default trace level is ClientDataSource.TRACE_ALL. You can choose the tracing level by calling the setTraceLevel(int level) method or by setting the traceLevel=value URL attribute:

    String url = "jdbc:derby://samplehost.sampledomain.com:1528/mydb" +
     ";traceFile=/u/user1/trace.out" +
     ";traceLevel=" +
     org.apache.derby.jdbc.ClientDataSource.TRACE_PROTOCOL_FLOWS;
    DriverManager.getConnection(url,"user1","secret4me");

Table 5. Available tracing levels and values

Trace level | Value
org.apache.derby.jdbc.ClientDataSource.TRACE_NONE | 0x0
org.apache.derby.jdbc.ClientDataSource.TRACE_CONNECTION_CALLS | 0x1
org.apache.derby.jdbc.ClientDataSource.TRACE_STATEMENT_CALLS | 0x2
org.apache.derby.jdbc.ClientDataSource.TRACE_RESULT_SET_CALLS | 0x4
org.apache.derby.jdbc.ClientDataSource.TRACE _DRIVER_CONFIGURATION | 0x10
org.apache.derby.jdbc.ClientDataSource.TRACE_CONNECTS | 0x20
org.apache.derby.jdbc.ClientDataSource.TRACE_PROTOCOL_FLOWS | 0x40
org.apache.derby.jdbc.ClientDataSource.TRACE _RESULT_SET_META_DATA | 0x80
org.apache.derby.jdbc.ClientDataSource.TRACE _PARAMETER_META_DATA | 0x100
org.apache.derby.jdbc.ClientDataSource.TRACE_DIAGNOSTICS | 0x200
org.apache.derby.jdbc.ClientDataSource.TRACE_XA_CALLS | 0x800
org.apache.derby.jdbc.ClientDataSource.TRACE_ALL | 0xFFFFFFFF;

To specify more than one trace level, use one of the following techniques:

• |  | Use bitwise OR operators ( | ) with two or more trace values. For example, to trace PROTOCOL flows and connection calls, specify this value for traceLevel:
    TRACE_PROTOCOL_FLOWS | TRACE_CONNECTION_CALLS
• |  | Use a bitwise complement operator ( ~ ) with a trace value to specify all except a certain trace. For example, to trace everything except PROTOCOL flows, specify this value for traceLevel:
    ~TRACE_PROTOCOL_FLOWS

For more information, see "traceLevel=value attribute" in the Java DB Reference Manual.
Network client driver examples
The following examples specify the user and password URL attributes. To enable user authentication, the property derby.connection.requireAuthentication must be set to true, otherwise, Derby does not require a user name and password. For details on how to enable user authentication, please see "Working with user authentication" in the Java DB Developer's Guide.
For a multi-user product, you would typically set it for the system in the derby.properties file for your server, since it is in a trusted environment. Below is a sample derby.properties file that conforms to these examples:

    derby.connection.requireAuthentication=true
    derby.authentication.provider=BUILTIN
    derby.user.judy=no12see

> Important: Derby's BUILTIN authentication mechanism is suitable only for development and testing purposes. It is strongly recommended that production systems rely on LDAP or a user-defined class for authentication. It is also strongly recommended that production systems protect network connections with SSL/TLS.
Example 1
The following example connects to the default server name localhost on the default port, 1527, and to the database sample.

    jdbc:derby://localhost:1527/sample;user=judy;password=no12see

Example 2
The following example specifies both Derby and Network Client driver attributes:

    jdbc:derby://localhost:1527/sample;create=true;user=judy;
    password=no12see

Example 3
This example connects to the default server name localhost on the default port, 1527, and includes the path in the database name portion of the URL.

    jdbc:derby://localhost:1527/c:/my-db-dir/my-db-name;user=judy;
    password=no12see

Example 4
The following example shows how to use the network client driver to connect the network client to the Network Server:

    String databaseURL = "jdbc:derby://localhost:1527/sample";
    //
    // Load Derby Network Client driver class.
    // If you are running on JDK 6 or higher, you do not
    // need to invoke Class.forName(). In that environment, the
    // network client driver loads automatically.
    //
    Class.forName("org.apache.derby.jdbc.ClientDriver");
    // Set user and password properties
    Properties properties = new Properties();
    properties.setProperty("user", "judy");
    properties.setProperty("password", "no12see");
    // Get a connection
    Connection conn = DriverManager.getConnection(databaseURL, properties);

Accessing the Network Server by using a DataSource object
The Network Server supports the Derby Network Client driver DataSource classes org.apache.derby.jdbc.ClientDataSource and org.apache.derby.jdbc.ClientConnectionPoolDataSource on all supported Java SE platforms.
If your client runs on the Java SE 6 platform, and if you want to use DataSource methods specific to the JDBC 4 API, use the DataSource classes named org.apache.derby.jdbc.ClientDataSource40 and org.apache.derby.jdbc.ClientConnectionPoolDataSource40.
If your client is running on the Java SE 6 platform, all connection objects returned from the DataSource will be JDBC 4 connection objects, whether or not you are using a DataSource whose name ends in "40".
Using statement caching
Derby supports JDBC statement caching, which can improve the performance of applications that use PreparedStatement or CallableStatement objects. Statement caching avoids the performance penalty incurred by going over the network from the client to the server to prepare a statement that has already been prepared on the same connection.
To use statement caching, you must use an org.apache.derby.jdbc.ClientConnectionPoolDataSource or an org.apache.derby.jdbc.ClientConnectionPoolDataSource40 object. After you instantiate this object, perform these steps:

1. |  | Specify the desired size of your statement cache by calling the setMaxStatements method on the DataSource object, specifying an argument greater than zero.
2. |  | Call the getPooledConnection method on the DataSource object to obtain a javax.sql.PooledConnection object (a physical connection).
3. |  | Call the javax.sql.PooledConnection.getConnection method to obtain a java.sql.Connection object (a logical connection).

After you obtain a connection, use either prepared statements or callable statements to interact with the database. Close each statement to return it to the cache after you finish using it. The statements you create are held in the cache on the client side and reused when needed.
See Statement caching example for a code example.
Use of the JDBC statement cache makes each physical connection use more memory. The amount depends on how many statements the connection is allowed to cache and how many statements are actually cached.
If you enable JDBC statement caching, error handling changes slightly. Some errors that previously appeared when the prepareStatement method was executed may now appear during statement execution. For example, suppose you query a table using a prepared statement that is then cached. If the table is deleted, the prepared statement that queries the table is not invalidated. If the query is prepared again on the same connection, the cached object is fetched from the cache, and the prepareStatement call seems to have succeeded, although the statement has not actually been prepared. When the prepared statement is executed, the error is detected on the server side, and the client is notified.
DataSource access examples
The following example uses org.apache.derby.jdbc.ClientDataSource to access the Network Server:

    org.apache.derby.jdbc.ClientDataSource ds =
       new org.apache.derby.jdbc.ClientDataSource();
    ds.setDatabaseName("mydb");
    ds.setCreateDatabase("create");
    ds.setUser("user");
    ds.setPassword("mypass");

    // The host on which Network Server is running
    ds.setServerName("localhost");

    // The port on which Network Server is listening
    ds.setPortNumber(1527);

    Connection conn = ds.getConnection();

Statement caching example
The following example uses org.apache.derby.jdbc.ClientConnectionPoolDataSource to access the Network Server and use JDBC statement caching:

    org.apache.derby.jdbc.ClientConnectionPoolDataSource cpds =
       new ClientConnectionPoolDataSource();

    // Set the number of statements the cache is allowed to cache.
    // Any number greater than zero will enable the cache.
    cpds.setMaxStatements(20);

    // Set other DataSource properties
    cpds.setDatabaseName("mydb");
    cpds.setCreateDatabase("create");
    cpds.setUser("user");
    cpds.setPassword("mypass");
    cpds.setServerName("localhost");
    cpds.setPortNumber(1527);

    // This physical connection will have JDBC statement caching enabled.
    javax.sql.PooledConnection pc = cpds.getPooledConnection();

    // Create a logical connection.
    java.sql.Connection con = pc.getConnection();

    // Interact with the database.
    java.sql.PreparedStatement ps = con.prepareStatement(
       "select * from myTable where id = ?");
    ...
    ps.close(); // Inserts or returns statement to the cache
    ...
    con.close();

    // The next logical connection can gain from using the cache.
    con = pc.getConnection();

    // This prepare causes a statement to be fetched from the local cache.
    PreparedStatement ps = con.prepareStatement(
       "select * from myTable where id = ?");
    ...

    // To dispose of the cache, close the connection.
    pc.close();

XA and the Network Server
Both the Derby embedded driver and the Network Server provide XA support. The Network Server provides DRDA level 7 support. DRDA clients that support XAMGR, such as the Derby network client, can send XA requests to the Network Server.
Using XA with the network client driver
You can access XA support for the Network Server by using the network client driver's XA DataSource interface.
The interface org.apache.derby.jdbc.ClientXADataSource is available on all supported Java SE platforms. If your client runs on the Java SE 6 platform, and if you want to use XA DataSource methods specific to the JDBC 4 API, use the DataSource named org.apache.derby.jdbc.ClientXADataSource40.
If your client is running on the Java SE 6 platform, all connection objects returned from the DataSource will be JDBC 4 connection objects, whether or not you are using the DataSource whose name ends in "40".
The following example illustrates how to obtain an XA connection with the network client driver:

    import org.apache.derby.jdbc.ClientXADataSource;
    import javax.sql.XAConnection;
    ...

    XAConnection xaConnection = null;
    Connection conn = null;

    ClientXADataSource ds = new ClientXADataSource();

    ds.setDatabaseName ("sample");
    ds.setCreateDatabase("create");

    ds.setServerName("localhost");
    ds.setPortNumber(1527);

    xaConnection = ds.getXAConnection("auser", "shhhh");

    conn = xaConnection.getConnection();

Using the Derby tools with the Network Server
The Derby tools ij and dblook work in embedded mode and client/server mode.
Using the Derby ij tool with the Network Server
To use the ij tool with the network client driver:

1. |  | Start ij in one of the following ways. For details, see "Starting ij" in the Java DB Tools and Utilities Guide.
a. |  | Use a script. Run the ij.bat script on Windows systems and the ij script on UNIX systems. These scripts are located in the $DERBY_HOME/bin directory.
b. |  | Run the ij tool using the $DERBY_HOME/lib/derbyrun.jar file.
    java -jar derbyrun.jar ij
c. |  | Run the ij tool by specifying the class name.
    java org.apache.derby.tools.ij
2. |  | Connect by specifying the URL:
    ij> CONNECT 'jdbc:derby://localhost:1527/sample'
    	USER 'judy' PASSWORD 'no12see';
See Network client driver examples for additional URL examples.

Using the Derby dblook tool with the Network Server
To use the dblook tool with the Network Client driver, make sure the Network Server is running (see Starting the Network Server), and then include the necessary Derby and Network Client driver connection attributes as part of the database URL, as in the following example:

    java org.apache.derby.tools.dblook -d 'jdbc:derby://localhost:1527/sample;
    user=user1;password=secret4me;'

For details on using the dblook tool, see the Java DB Tools and Utilities Guide.
Differences between running Derby in embedded mode and using the Network Server
This section describes the differences between running Derby in embedded mode and using the Network Server. Note that there may be undocumented differences that have not yet been identified.
Differences between the embedded client and the network client driver
The following are known differences that exist between the Derby embedded driver and the network client driver. Note that there may be undocumented differences that have not yet been identified. Some differences with the network client may be changed in future releases to match the embedded driver functionality.

• |  | Error messages and SQLStates can differ between the network client and embedded driver. Some SQLStates may be null when using the network client, particularly for data conversion errors.
• |  | Multiple SQL exceptions and warnings will only return the SQLState of the first exception when using the network client. The text of the additional exceptions will be appended to the text of the first exception. See Error message differences.
• |  | Treatment of error situations encountered during batch processing with java.sql.Statement, java.sql.PreparedStatement and java.sql.CallableStatement is different. With the embedded driver processing stops when an error is encountered; with the network client driver processing continues, but an appropriate value as defined in the java.sql.Statement api is returned in the resulting update count array.
• |  | To use an encrypted user id and password, you need to have the IBM's Java Cryptography Extension (JCE) Version 1.2.1 or later.

Updatable Result Sets
The functionality of updatable result sets in a server environment are similar to an embedded environment in Derby, with the exception of the following differences:

• |  | The Network Client requires that there be at least one column in the select list from the target table. For example, the following statement will fail in a server environment:
    select 1, 2 from t1 for update of c11
The Network Client driver looks at both of the columns in the select list and cannot determine the target table for update/delete by looking at the column metadata. This requirement is not necessary in an embedded environment.
• |  | The embedded driver allows for statement name changes when there is an open result set on the statement object. This is not supported in a server environment.

Other differences between updatable result sets in a server or embedded environment can be found in the following table.
Table 6. Comparison of updatable result sets features in server and embedded environments

Embedded environment | Server environment
updateBytes on CHAR, VARCHAR, LONG VARCHAR datatypes supported. | Not supported
updateTime on TIMESTAMP datatypes supported. | Not supported
updateClob and updateBlob supported. | Not supported

Error message differences
The Network Server reports only the first error or warning message if multiple errors or warnings occur for a given statement. For example:

    ij> create table ai (x int, y int generated always as identity
    	(increment by 200000000));
    ij> insert into ai (x) values (1),(2),(3),(4),(5),(6),(7),
    (8),(9),(10),(11),(12),(13),(14),(15),(16),(17),(18),(19);

The Network Server generates the following error message and appends the exception message to the error:

    ERROR 42Z24: Overflow occurred in identity for column 'Y' in table 'AI':
    SQLSTATE: 22003: The resulting value is outside the range
    for the data type INTEGER.

The Derby embedded driver, however, would generate two SQL exceptions:

    ERROR 42Z24: Overflow occurred in identity for column 'Y' in table 'AI'.

    ERROR 22003: The resulting value is outside the range for the data type INTEGER.

This is because the network client driver reports only one SQLException or one SQLWarning per statement.
User authentication differences
When running Derby in embedded mode or when using the Derby Network Server, you can enable or disable server-side user authentication. However, when using the Network Server, the default security mechanism (CLEAR_TEXT_PASSWORD_SECURITY) requires that you supply both the user name and password.
In addition to the default user name and password security mechanism, org.apache.derby.jdbc.ClientDataSource.CLEAR_TEXT_PASSWORD_SECURITY, Derby Network Server supports the following security properties:

• |  | UserID (org.apache.derby.jdbc.ClientDataSource.USER_ONLY_SECURITY) When using this mechanism, you must specify only the user property. All other mechanisms require you to specify both the user name and the password.
• |  | Encrypted UserID and encrypted password (org.apache.derby.jdbc.ClientDataSource.ENCRYPTED_USER_AND_PASSWORD_SECURITY) When using this mechanism, both password and user id are encrypted.
• |  | Strong password substitution (org.apache.derby.jdbc.ClientDataSource.STRONG_PASSWORD_SUBSTITUTE_SECURITY) When using this mechanism, a strong password substitute is generated and used to authenticate the user with the network server. The original password is never sent in any form across the network.

The user's name that is specified upon connection is the default schema for the connection, if a schema with that name exists. See the Java DB Developer's Guide for more information on schema and user names.
If you specify any other security mechanism, you will receive an exception.
To change the default, you can specify another security mechanism either as a property or on the URL (using the securityMechanism=value attribute) when making the connection. For details, see Network client security and "securityMechanism=value attribute" in the Java DB Reference Manual.
Whether the security mechanism you specify for the client actually takes effect depends upon the setting of the derby.drda.securityMechanism property for the Network Server. If the derby.drda.securityMechanism property is set, the Network Server accepts only connections that use the security mechanism specified by the property setting. If the derby.drda.securityMechanism property is not set, clients can use any valid security mechanism. For details, see derby.drda.securityMechanism property.
Security mechanism options when user authentication is enabled on the Network Server:
When user authentication is enabled in Derby, you can use any of the following security mechanisms:

• |  | Clear text user name and password security, the default
• |  | Strong password substitute security
• |  | Encrypted user name and password security

Security mechanism options when user authentication is disabled on the Network Server:
When user authentication is turned off in Derby, you can use any of the security mechanism options.
You must provide a user and password for all security mechanisms except USER_ONLY_SECURITY. However, because user authentication is disabled in the Derby server, the user name and password that you supply does not have to be one recognized as valid by Derby.
Enabling the encrypted user ID and password security mechanism:
To use the encrypted user ID and password security mechanism, you need a Java environment with a JCE (Java Cryptography Extension) which supports the Diffie-Hellman algorithm with a public prime of 256 bits. The Sun Java Platform, Standard Edition, Version 1.4 (J2SE) and later requires a public prime of 512 bits or more. An alternative mechanism if the 256 bit public prime is not supported, is STRONG_PASSWORD_SUBSTITUTE_SECURITY.
To use the encrypted user id and password security mechanism during JDBC connection using the network client, specify the securityMechanism in the connection property.
Note: If an encrypted database is booted in the Network Server, users can connect to the database without giving the bootPassword. The first connection to the database must provide the bootPassword, but all subsequent connections do not need to supply it. To remove access from the encrypted database, use the shutdown=true option to shut down the database.
Differences in JDBC 3.0 methods
The following JDBC 3.0 methods are supported only with the Derby embedded driver. Attempts to call these methods with the network client driver will result in a "not implemented" error.

    Connection.prepareStatement(String sql, String[] columnNames)
    Connection.prepareStatement(String sql, int[] columnIndexes)

    Statement.execute(String sql, String[] columNames)
    Statement.execute(String sql, int[] columIndexes)
    Statement.executeUpdate(String sql, String[] columnNames)
    Statement.executeUpdate(String sql, int[] columnIndexes)

For more on the use of these methods, see the sections "java.sql.Connection interface: supported JDBC 3.0 methods", "java.sql.Statement interface: supported JDBC 3.0 methods", and "Autogenerated keys" in the Java DB Reference Manual.
Differences using the Connection.setReadOnly method
In the embedded mode, when the Connection.setReadOnly method has true as the parameter, the connection is marked as a read-only connection. When using a Network Server, the Connection.setReadOnly(true) method is ignored and the connection is not marked as a read-only connection.
Setting port numbers
By default, Derby using the Network Server listens on TCP/IP port number 1527. If you want to use a different port number, you can specify it on the command line when starting the Network Server. For example:

    java org.apache.derby.drda.NetworkServerControl start -p 1088

1. |  | However, it is better to specify the port numbers by using any of the following methods
• |  | Change the startNetworkServer.bat or startNetworkServer.ksh scripts
• |  | Use the derby.drda.portNumber property in derby.properties

See Starting the Network Server for more information.
Managing the Derby Network Server
The Derby Network Server can be run in either of these configurations:

• |  | As a stand-alone server, in which case it is an independent Java process embedding the Derby database engine
• |  | As an embedded server, in which case it is embedded within another Java application, and both the Network Server framework and the Derby database engine are loaded by the Java application

You can use Java Management Extensions (JMX) technology to monitor and manage Derby and the Network Server. For information on how to do this, visit the wiki page http://wiki.apache.org/db-derby/DerbyJMX and refer to the API documentation for the packages org.apache.derby.mbeans and org.apache.derby.mbeans.drda. For information on JMX technology, see http://java.sun.com/javase/technologies/core/mntr-mgmt/javamanagement/.
You can manage the Network Server by using shell scripts, the command line, or the Network Server API. The Network Server can also be managed remotely from a web server by using a servlet interface. See Managing the Derby Network Server remotely by using the servlet interface for information about starting and shutting down the Network Server using the servlet interface.
Overview
You start the Derby Network Server using the command line or using the Derby Server API. (Derby provides scripts for you to use to start the server from the command line.) Before starting the server, you will probably set certain Derby and Network Server properties.
Using the NetworkServerControl API
You need to create an instance of the NetworkServerControl class if you are using the API. There are four constructors for this class:
Note: Before enabling connections from other systems, ensure that you are running under a security manager.

• |  | NetworkServerControl() This constructor creates an instance that listens either on the default port (1527) or the port that is set by the derby.drda.portNumber property. It will also listen on the host set by the derby.drda.host property or the loopback address if the property is not set. This is the default constructor; it does not allow remote connections. It is equivalent to calling NetworkServerControl(InetAddress.getByName("localhost"),1527) if no properties are set.
• |  | NetworkServerControl(InetAddress address, int portNumber) This constructor creates an instance that listens on the specified portNumber on the specified address. The InetAddress will be passed to ServerSocket. NULL is an invalid address value. The following examples show how you might allow Network Server to accept connections from other hosts:
    //accepts connections from other hosts on an IPv4 system
    NetworkServerControl serverControl =
      new NetworkServerControl(InetAddress.getByName("0.0.0.0"),1527);
    //accepts connections from other hosts on an IPV6 system
    NetworkServerControl serverControl =
      new NetworkServerControl(InetAddress.getByName("::"),1527);
• |  | NetworkServerControl(String userName, String password) If a network server should run with user authentication, certain operations like NetworkServerControl.shutdown() require that you provide user credentials. This constructor creates an instance with user credentials, which are then used for operations that require them. In all other aspects, this constructor behaves like NetworkServerControl().
• |  | NetworkServerControl(InetAddress address, int portNumber, String userName, String password) This constructor creates an instance with user credentials, which are then used for operations that require them. In all other aspects, this constructor behaves like NetworkServerControl(InetAddress address, int portNumber).

Setting Network Server properties
You can specify Network Server properties in three ways:

• |  | On the command line
• |  | In the .bat or .ksh files (loading the properties by executing java -D)
• |  | In the derby.properties file.

Properties in the command line or in the .bat or .ksh files take precedence over the properties in the derby.properties file. Arguments included on commands that are issued on the command line take precedence over property values.
derby.drda.host property
Causes the Network Server to listen on a specific network interface. This property allows multiple instances of Network Server to run on a single machine, each using its own unique host:port combination. The host needs to be set to enable remote connections. By default, the Network Server will listen only on the loopback address. If the property is set to 0.0.0.0, Network Server will listen on all interfaces. Ensure that you are running under the security manager and that user authorization is enabled before you enable remote connections with this property.
Syntax

    derby.drda.host=hostname

Default
If no host name is specified, the Network Server listens on the loopback address of the current machine (localhost).
Example

    derby.drda.host=myhost

Static or dynamic
Static. You must restart the Network Server for changes to take effect.
derby.drda.keepAlive property
Indicates whether SO_KEEPALIVE is enabled on sockets. The keepAlive mechanism is used to detect when clients disconnect unexpectedly. A keepalive probe is sent to the client if a long time (by default, more than two hours) passes with no other data being sent or received. The derby.drda.keepAlive property is used to detect and clean up connections for clients on powered-off machines or clients that have disconnected unexpectedly.
If the property is set to false, Derby will not attempt to clean up disconnected clients. The keepAlive mechanism might be disabled if clients need to resume work without reconnecting even after being disconnected from the network for some time. To disable keepAlive probes on Network Server connections, set this property to false.
Syntax

    derby.drda.keepAlive=[true|false]

Default
True.
Example

    derby.drdra.keepAlive=false

Static or dynamic
Static. You must restart the Network Server for changes to take effect.
derby.drda.logConnections property
Indicates whether to log connections. Also controls the logging of the connection number. Connection number tracing, if enabled, goes to both the derby.log file and the network server console.
Syntax

    derby.drda.logConnections=[true|false]

Default
False.
Example

    derby.drda.logConnections=true

Static or dynamic
Dynamic. System values can be changed by using commands or the servlet interface after the Network Server has been started.
derby.drda.maxThreads property
Use the derby.drda.maxThreads property to set a maximum number of connection threads that Network Server will allocate. If all of the connection threads are currently being used and the Network Server has already allocated the maximum number of threads, the threads will be shared by using the derby.drda.timeSlice property to determine when sessions will be swapped.
Syntax

    derby.drda.maxThreads=numthreads

Default
0
Example

    derby.drda.maxThreads=50

Static or dynamic
Static. You must restart the Network Server for changes to take effect.
derby.drda.minThreads property
Use the derby.drda.minThreads property to set the minimum number of connection threads that Network Server will allocate. By default, connection threads are allocated as needed.
Syntax

    derby.drda.minThreads=numthreads

Default
0
Example

    derby.drda.minThreads=10

Static or dynamic
Static. You must restart the Network Server for changes to take effect.
derby.drda.portNumber property
Indicates the port number to use.
Syntax

    derby.drda.portNumber=portnumber

Default
If no port number is specified, 1527 is the default.
Example

    derby.drda.portNumber=1110

Static or dynamic
Static. You must restart the Network Server for changes to take effect.
derby.drda.securityMechanism property
The derby.drda.securityMechanism property restricts the client connections based on the security mechanism.
If the derby.drda.securityMechanism property is set to a valid mechanism, the Network Server accepts only connections which use that security mechanism. No other types of connections are accepted. If the derby.drda.securityMechanism property is not set, the Network Server accepts any connection which uses a valid security mechanism.
Syntax

    derby.drda.securityMechanism = [
        USER_ONLY_SECURITY |
        CLEAR_TEXT_PASSWORD_SECURITY |
        ENCRYPTED_USER_AND_PASSWORD_SECURITY |
        STRONG_PASSWORD_SUBSTITUTE_SECURITY
    ]

Default
None.
Example

    derby.drda.securityMechanism=USER_ONLY_SECURITY

The server that runs with this setting accepts only client connections with the USER_ONLY_SECURITY value.
Static or dynamic
Static. You must restart the Network Server for the changes that are associated with this property to take effect.
derby.drda.sslMode property
The derby.drda.sslMode property indicates whether the client connection is encrypted or not, and whether certificate based peer authentication is enabled.
Syntax

    derby.drda.sslMode = [ off | basic | peerAuthentication ]

Default
off
Example

    derby.drda.sslMode=basic

The server that runs with this setting accepts client connections encrypted with SSL.
Static or dynamic
Static. You must restart the Network Server for the changes that are associated with this property to take effect.
derby.drda.startNetworkServer property
Use the derby.drda.startNetworkServer property to simplify embedding the Network Server in your Java application. When you set derby.drda.startNetworkServer to true, the Network Server will automatically start when you start Derby (in this context, Derby will start when the embedded driver is loaded). Only one Network Server can be started in a JVM.
NOTE: If you start the Network Server with this property set to true, the Network Server will stop when your application ends or when you stop it by other means (e.g. by using the Java API, the command line interface, or by shutting down the Derby system), whichever comes first.
Syntax

    derby.drda.startNetworkServer=[true | false]

Default
False.
Example

    derby.drda.startNetworkServer=true

Static or dynamic
Static. You must shut down the Network Server and restart Derby for this change to take effect.
derby.drda.streamOutBufferSize property
Configure size of buffer for streaming blob/clob from server to client. If the configured size is 0 or less, the buffer is not placed.
Note:
This configuration is used when optimizing streaming blob/clob from server to client.
If there were found many small packets, of which sizes are much lower than maximum size of packet possible in the network, it will improve performance of streaming to setting this configuration.
Recommended value of this configuration is maximum packet size possible in the network minus appropriate size for header.
Syntax

    derby.drda.streamOutBufferSize=size of buffer

Default
0
Example

    derby.drda.streamOutBufferSize=1024

Static or dynamic
Dynamic. System values can be changed by using commands or the servlet interface after the Network Server has been started.
derby.drda.timeSlice property
Use the derby.drda.timeSlice property to set the number of milliseconds that each connection will use before yielding to another connection. This property is relevant only if the derby.drda.maxThreads property is set to a value greater than zero.
Syntax

    derby.drda.timeSlice=milliseconds

Default
0
Example

    derby.drda.timeSlice=2000

Static or dynamic
Static. You must restart the Network Server for changes to take effect.
derby.drda.traceAll property
Turns tracing on for all sessions.
Syntax

    derby.drda.traceAll=[true|false]

Default
False.
Example

    derby.drda.traceAll=true

Static or dynamic
Dynamic. System values can be changed by using commands or the servlet interface after the Network Server has been started.
derby.drda.traceDirectory property
Indicates the location of tracing files.
Security Considerations
The Network Server will attempt to create the trace directory (and any parent directories) if they do not exist. This will require that the Java security policy for derbynet.jar permits verification of the existence of the named trace directory and all necessary parent directories. For each directory created, the policy must allow

        permission java.io.FilePermission "<directory>", "read,write";

and for the trace directory itself, the policy must allow

        permission java.io.FilePermission "<tracedirectory>${/}-", "write";

See Customizing the Network Server's security policy for information about customizing the Network Server's security policy.
Syntax

    derby.drda.traceDirectory=tracefiledirectory

Default
If the derby.system.home property has been set, it is the default. Otherwise, the default is the current directory.
Example

    derby.drda.traceDirectory=c:/Derby/trace

Static or dynamic
Dynamic. System values can be changed by using commands or the servlet interface after the Network Server has been started.
Verifying Startup
To verify that the Derby Network Server is currently running, use the ping command.
You can use the ping command in the following ways:

• |  | You can use the scripts NetworkServerControl.bat for Windows systems or NetworkServerControl.ksh for UNIX systems with the ping command. For example:
    NetworkServerControl ping [-h <hostname>;] [-p <portnumber>]
• |  | You can use the NetworkServerControl command:
    java org.apache.derby.drda.NetworkServerControl
       ping [-h <hostname>] [-p <portnumber>]
• |  | You can use the NetworkServerControl API to verify startup from within a Java application:
    ping();

The following example uses a method to verify startup. It will try to verify for the specified number of seconds:

    private static boolean isServerStarted(NetworkServerControl server, int ntries)
    	{
    		for (int i = 1; i <= ntries; i ++)
    		{
    			try {
    				Thread.sleep(500);
    				server.ping();
    				return true;
    			}
    			catch (Exception e) {
    				if (i == ntries)
    					return false;
    			}
    		}
    		return false;
    	}

Managing the Derby Network Server remotely by using the servlet interface
You can use the servlet interface to manage the Network Server remotely. To use the servlet interface, the servlet must be registered with an Application Server, and derby.system.home must be known to the Application Server.
A Web application archive (WAR) file, derby.war, for the Derby Network Server is available in $DERBY_HOME/lib. This file registers the Network Server's servlet at the relative path /derbynet. See the documentation for your Application Server for instructions on how to install it.
For example, if derby.war is installed in WebSphere Application Server with a context root of derby, the URL of the server is:

    http://<server>[:port]/derby/derbynet

Notes:

• |  | A servlet engine is not part of the Network Server.
• |  | When the Network Server is started by the servlet interface, shutting down the Application Server also shuts the Network Server down, since both run in the same JVM.

The servlet takes the following optional configuration parameters:
host
Specifies the host name to be used by the Network Server. See the Security Considerations section below.
portNumber
Specifies the port number to be used by the Network Server.
startNetworkServerOnInit
Specifies that the Network Server is to be started when the servlet is initialized.
tracingDirectory
Specifies the location for trace files. If the tracing directory is not specified, the traces are placed in derby.system.home.
Security Considerations
For general security considerations for the Network Server, see Network Server security.
The "host" parameter allows configuration of the host name that will be used for the listening socket for network connections. By default, the Network Server will listen to requests only on the loopback address, which means that it will only accept connections from the local host. Changing this value could expose the server to external connections, which raises security concerns, so before using the "host" parameter, you should run under the Java security manager and enable user authentication.
This section describes the servlet pages.
Start-up page
Use the start-up page to start the server.
In addition to starting the Network Server, you can use the startup page to perform the following actions:

• |  | Turn logging on when the server is started.
• |  | Turn tracing on for all sessions when the server is started.

Running page
If the Network Server is running (whether it was started by initializing the servlet or in some other manner), the running page is displayed. The running page indicates whether logging is on or off, whether tracing is on or off, and if tracing is on, indicates for which session.
You can use the running page to stop the server and turn logging and tracing on or off. The following options are available from the running page:

• |  | Start or stop logging.
• |  | Start or stop tracing all sessions.
• |  | Specify session to trace. (If you choose this option, the Trace session page is displayed.)
• |  | Change tracing directory (If you choose this option, the Trace directory page is displayed.)
• |  | Specify threading parameters for Network Server. (If you choose this option, the Thread parameters page is displayed.)
• |  | Stop the Network Server.

Trace session page
If on the running page you choose to specify a session to trace, this page is displayed. You must enter the Session ID.
You are given the option to turn tracing on or off or return to the previous menu. When you push the Trace On/Off button, information indicating the current tracing state is displayed.
Trace directory page
This page is displayed if the you choose to change the tracing directory on the Running page. You must enter the Trace Directory.
You can either set a tracing directory, or you can return to the previous menu. Additional information is displayed that indicates the current tracing directory when you push the Set Directory button.
Set Network Server parameters
The first page is displayed if the thread parameter button is pressed. Use this page to set the new parameters. Enter the following information:

• |  | New maximum number of threads
• |  | New thread time slice

If either the maximum threads or time slice parameters are left blank, that value is left unchanged from the current setting.
Click Set Network Server parameters to display the updated values for the maximum threads and the time slice parameters.
Derby Network Server advanced topics
This section discusses several advanced topics for users of the Derby Network Server.
Network Server security
By default, the Derby Network Server will only listen on the localhost. Clients must use the localhost host name to connect. By default, clients cannot access the Network Server from another host. To enable connections from other hosts, set the derby.drda.host property, or start the Network Server with the -h option in the java org.apache.derby.drda.NetworkServerControl start command.
In the following example the server will listen only on localhost and clients cannot access the server from another host.

    java org.apache.derby.drda.NetworkServerControl start

In the following example, the server runs on host machine sampleserver.sampledomain.com and also listens for clients from other hosts. Clients must specify the server in the URL or DataSource as sampleserver.sampledomain.com:

    java org.apache.derby.drda.NetworkServerControl start
       -h sampleserver.sampledomain.com

To start the Network Server so that it will listen on all interfaces, start with an IP address of 0.0.0.0, shown in the following example:

    java org.apache.derby.drda.NetworkServerControl start -h 0.0.0.0

A server that is started with the -h 0.0.0.0 option will listen to client requests that originate from both localhost and from other machines on the network.
However, administrative commands (for example, org.apache.derby.drda.NetworkServerControl shutdown) can run only on the host where the server was started, even if the server was started with the -h option.
Running the Network Server under the security manager
By default, the Network Server boots with a Basic security policy. You are encouraged to customize this policy to fit the security needs of your application and its runtime environment. You may also run the Network Server without a security manager, although this is not recommended.
Basic Network Server security policy
If you boot the Network Server without specifying a security manager, the Network Server will install a default Java security manager enforcing a Basic policy. This happens if you boot the Network Server as your VM's entry point, e.g.:

    java org.apache.derby.drda.NetworkServerControl start ...

Note that you should run your Network Server with user authentication enabled. For details on how to enable user authentication, please see "Working with user authentication" in the Java DB Developer's Guide.
Some of your application code may run as procedures and functions which you have declared using the CREATE PROCEDURE and CREATE FUNCTION statements. You will need to add privileged blocks to your declared procedures and functions if they perform sensitive operations such as file and network i/o, classloading, system property reading, etc.
If for some reason you do not want to run your client/server application under a security manager, you may override the Network Server's impulse to install a default policy. For details, see Running the Network Server without a security policy.
Note that the Network Server attempts to install a security manager only if you boot the server as the entry point of your VM. The Network Server will not attempt to install a security manager if you start the server from your application using the programmatic API described in the following section: Starting the Network Server from a Java application.
You will find a template security policy in the Derby distribution at demo/templates/server.policy. Most likely, you will want to customize this policy. For example, probably you will want to restrict the server's liberal file i/o permissions which let the server backup/restore and export/import to or from any location in the local file system. For details on how to customize the Template policy, please see Customizing the Network Server's security policy. The following example is a copy of the Basic policy:

    grant codeBase "${derby.install.url}derby.jar"
    {
    //
    // These permissions are needed for everyday, embedded Derby usage.
    //
      permission java.lang.RuntimePermission "createClassLoader";
      permission java.util.PropertyPermission "derby.*", "read";
      // The next two properties are used to determine if the VM is 32 or 64 bit.
      permission java.util.PropertyPermission "sun.arch.data.model", "read";
      permission java.util.PropertyPermission "os.arch", "read";
      permission java.util.PropertyPermission "user.dir", "read";
      permission java.util.PropertyPermission "derby.storage.jvmInstanceId",
          "write";
      permission java.io.FilePermission "${derby.system.home}","read";
      permission java.io.FilePermission "${derby.system.home}${/}-", "read,write,delete";

    //
    // This permission lets you backup and restore databases
    // to and from arbitrary locations in your file system.
    //
    // This permission also lets you import/export data to and from
    // arbitrary locations in your file system.
    //
    // You may want to restrict this access to specific directories.
    //
      permission java.io.FilePermission "<<ALL FILES>>", "read,write,delete";
    };

    grant codeBase "${derby.install.url}derbynet.jar"
    {
    //
    // This permission lets the Network Server manage connections from clients.
    //

    // Accept connections from any host. Derby is listening to the host
    // interface specified via the -h option to "NetworkServerControl
    // start" on the command line, via the address parameter to the
    // org.apache.derby.drda.NetworkServerControl constructor in the API
    // or via the property derby.drda.host; the default is localhost.
    // You may want to restrict allowed hosts, e.g. to hosts in a specific
    // subdomain, e.g. "*.acme.com".

      permission java.net.SocketPermission "*", "accept";
    };

Customizing the Network Server's security policy
The Network Server's Basic security policy is documented in the section Basic Network Server security policy. Most likely, you will want to customize your own security policy. For example, you might want to restrict the server's liberal file i/o permissions which let the server backup/restore and export/import to or from any location in the local file system. Customizing the security policy is simple:

• |  | A template policy lives in the Derby distribution at demo/templates/server.policy. Copy the file from this location to your own file, say myCustomized.policy. All of the following edits take place in your custom file.
• |  | Replace the ${derby.install.url} variable with the location of the Derby jars in your local file system.
• |  | Replace the ${derby.system.home} variable with the location of your Derby system directory. Alternatively, rather than replacing this variable, you can simply set the value of the derby.system.home system property when you boot the server.
• |  | You may want to restrict the socket permission for derbynet.jar, which by default accepts connections from any host ("*"). Note that the special wildcard address "0.0.0.0" is not understood by SocketPermission, even though Derby accepts this wildcard as a valid value for accepting connections on all network interfaces (IPv4).
• |  | Refine the file permissions needed by backup/restore, import/export, and the loading of application jars.

The following example is a copy of a sample, customized policy file:

    grant codeBase "file:/usr/local/share/sw/derby/lib/derby.jar"
    {
    //
    // These permissions are needed for everyday, embedded Derby usage.
    //
      permission java.lang.RuntimePermission "createClassLoader";
      permission java.util.PropertyPermission "derby.*", "read";
      // The next two properties are used to determine if the VM is 32 or 64 bit.
      permission java.util.PropertyPermission "sun.arch.data.model", "read";
      permission java.util.PropertyPermission "os.arch", "read";
      permission java.util.PropertyPermission "user.dir", "read";
      permission java.io.FilePermission "/usr/local/shoppingCartApp/databases","read";
      permission java.io.FilePermission "/usr/local/shoppingCartApp/databases/-",
          "read,write,delete";
      permission java.util.PropertyPermission "derby.storage.jvmInstanceId",
          "write";

    //
    // This permission lets a DBA reload the policy file while the server
    // is still running. The policy file is reloaded by invoking the
    // SYSCS_UTIL.SYSCS_RELOAD_SECURITY_POLICY() system procedure.
    //
      permission java.security.SecurityPermission "getPolicy";

    //
    // This permission lets you backup and restore databases
    // to and from a selected branch of the local file system:
    //
      permission java.io.FilePermission "/usr/local/shoppingCartApp/backups/-", "read,write,delete";
    //
    // This permission lets you import data from
    // a selected branch of the local file system:
    //
      permission java.io.FilePermission "/usr/local/shoppingCartApp/imports/-", "read";
    //
    // This permission lets you export data to
    // a selected branch of the local file system:
    //
      permission java.io.FilePermission "/usr/local/shoppingCartApp/exports/-", "write";
    //
    // This permission lets you load your databases with jar files of
    // application code
    //
      permission java.io.FilePermission "/usr/local/shoppingCartApp/lib/*", "read";
    };

    grant codeBase "file:/usr/local/share/sw/derby/lib/derbynet.jar"
    {
    //
    // This permission lets the Network Server manage connections from clients
    // originating from the localhost, on any port.
    //
      permission java.net.SocketPermission "localhost:0-", "accept";
    };

After customizing the Basic policy, you may bring up the Network Server as follows:

    java -Djava.security.manager -Djava.security.policy=/usr/local/shoppingCartApp/lib/myCustomized.policy org.apache.derby.drda.NetworkServerControl start -h localhost

Running the Network Server without a security policy
You may override the Network Server's impulse to install a security manager if, for some reason, you need to run your application outside Java's security protections.
CAUTION: You incur a severe security risk by opening up the server to all clients without limiting access via user authentication and a security policy.
Use the -noSecurityManager option to force the Network Server to come up without a security manager. E.g.:

    java org.apache.derby.drda.NetworkServerControl start -h localhost -noSecurityManager

Running the Network Server with User Authentication
By default, the Network Server boots with user authentication disabled. However, it is strongly recommended that you run your Network Server with user authentication enabled. For details on how to enable user authentication, please see "Working with user authentication" in the Java DB Developer's Guide.
Network encryption and authentication with SSL/TLS
By default, all Derby network traffic is unencrypted, with the exception of user names and user passwords which may be encrypted separately (See Network client security). There is also no network layer access control mechanism. For deployment scenarios where these are possible security issues, Derby Network Server supports network security with Secure Socket Layer/Transport Layer Security (SSL/TLS).
With SSL/TLS, the client/server communication protocol is encrypted and both the client and the server may independently of each other require certificate based authentication of the other part.
It is assumed that the reader is somewhat familiar with SSL, key pairs and certificates. This documentation is also based on the Java Development Kit (JDK) and its keytool application.
For the remainder of this section, the term SSL is used for SSL/TLS and the term peer is used for the other part of the communication (The server's peer is the client and vice versa).
SSL for Derby (both for client and for server) operates in three possible modes:
off
The default, no SSL encryption
basic
SSL encryption, no peer authentication
peerAuthentication
SSL encryption and peer authentication
Peer authentication may be set either on the server or on the client or on both. Peer authentication means that the other side of the SSL connection is authenticated based on a trusted certificate installed locally.
Alternatively, a Certification Authority (CA) certificate may be installed locally and the peer has a certificate signed by that authority. How to achieve this is not descibed in this document. Consult your Java environment documentation for details on this.
Attention: If a plaintext client tries to communicate with an SSL server or an SSL client tries to communicate with a plaintext server, the plaintext side of the communication will see the SSL communication as noise and report protocol errors.
Key and certificate handling
For SSL operation, the server always needs a key pair. If the server runs in peer authentication mode (the server authenticates the clients), then each client needs its own key pair. In general, if one end of the communication wants to authenticate its partner, then the first end needs to install a certificate generated by the partner.
The key pair is located in a file which is called a key store and the JDK's SSL provider needs the system properties javax.net.ssl.keyStore and javax.net.ssl.keyStorePassword to access the key store.
The certificates of trusted parties are installed in a file called a trust store. The JDK's SSL provider needs the system properties javax.net.ssl.trustStore and javax.net.ssl.trustStorePassword to access the trust store.
Key pair generation
Key pairs are generated with keytool -genkey. The simplest way to generate a key pair is to do

    keytool -genkey <alias> -keystore <keystore>

ketool will prompt for needed information like identity details and passwords.
Consult the JDK documentation for more information on keytool.
Certificate generation
Certificates are generated with keytool -export like this:

    keytool -export -alias <alias> -keystore <keystore> \
            -rfc -file <certificate file>

The certificate file may then be distributed to the relevant parties.
Certificate installation
Installation of a certificate in a trust store is done with keytool -import like this:

    keytool -import -alias <alias> -file <certificate file> \
            -keystore <trust store>

Examples
Generate the server key pair:

    keytool -genkey -alias myDerbyServer -keystore serverKeyStore.key

Generate a server certificate:

    keytool -export -alias myDerbyServer -keystore serverKeyStore.key \
            -rfc -file myServer.cert

Generate a client key pair:

    keytool -genkey -alias aDerbyClient -keystore clientKeyStore.key

Generate a client certficate:

    keytool -export -alias aDerbyClient -keystore clientKeyStore.key \
            -rfc -file aClient.cert

Install a client certificate in the server's trust store:

    keytool -import -alias aDerbyClient -file aClient.cert
            -keystore serverTrustStore.key

Install the server certificate in a client's trust store:

    keytool -import -alias myDerbyServer -file myServer.cert
            -keystore clientTrustStore.key

Starting the server with SSL/TLS
For server SSL/TLS, a server key pair needs to be generated. If the server is going to do client authentication, the client sertificates need to be installed in the trust store. These operations are described in Key and certificate handling.
SSL at the server side is activated with the property derby.drda.sslMode (default off) or the -ssl option for the server start command.
Starting the server with basic SSL encryption
When the SSL mode is set to basic, the server will only accept SSL encrypted connections.
The properties javax.net.ssl.keyStore and javax.net.ssl.keyStorePassword need to be set with the proper values.
Example:

    java -Djavax.net.ssl.keyStore=serverKeyStore.key \
         -Djavax.net.ssl.keyStorePassword=qwerty \
         -jar derbyrun.jar server start -ssl basic

Starting a server which authenticates clients
When the server's SSL mode is set to peerAuthentication, then the server authenticates its clients' identity in addition to encrypting network traffic. In this situation, the server's trust store must contain a certificate for each client which will connect.
The javax.net.ssl.trustStore and javax.net.ssl.trustStorePassword need to be set in addition to the properties above.
See Running the client with SSL/TLS for client settings when the server does client authentication
Example:

    java -Djavax.net.ssl.keyStore=serverKeyStore.key \
         -Djavax.net.ssl.keyStorePassword=qwerty \
         -Djavax.net.ssl.trustStore=serverTrustStore.key \
         -Djavax.net.ssl.trustStorePassword=qwerty \
         -jar derbyrun.jar server start -ssl peerAuthentication

Running the client with SSL/TLS
Basic SSL encryption on the client is enabled either by the URL attribute ssl, the property ssl or the datasource attribute ssl set to basic.
Example:

    Connection c =
       getConnection("jdbc:derby://myhost:1527/db;ssl=basic");

Running a client which authenticates the server
If the client wants to authenticate the server, then the client's trust store must contain the server's certificate. See Key and certificate handling.
Client SSL with server authentication is enabled by the URL attribute ssl or the property ssl set to peerAuthentication. In addition, the system properties javax.net.ssl.trustStore and javax.net.ssl.trustStorePassword need to be set.
Example:

        System.setProperty("javax.net.ssl.trustStore","clientTrustStore.key");
        System.setProperty("javax.net.ssl.trustStorePassword","qwerty");
        Connection c =
           getConnection("jdbc:derby://myhost:1527/db;ssl=peerAuthentication");

Running the client when the server does client authentication
If the server does client authentication, the client will need a key pair and a client certificate which is installed in the server's trust store, See Key and certificate handling.
The client needs to set javax.net.ssl.keyStore and javax.net.ssl.keyStorePassword.
Example:

        System.setProperty("javax.net.ssl.keyStore","clientKeyStore.key");
        System.setProperty("javax.net.ssl.keyStorePassword","qwerty");
        Connection c =
           getConnection("jdbc:derby://myhost:1527/db;ssl=basic");

Running the client when both parties do peer authentication
This is a combination of the two last variants.
Example:

        System.setProperty("javax.net.ssl.keyStore","clientKeyStore.key");
        System.setProperty("javax.net.ssl.keyStorePassword","qwerty");
        System.setProperty("javax.net.ssl.trustStore","clientTrustStore.key");
        System.setProperty("javax.net.ssl.trustStorePassword","qwerty");
        Connection c =
           getConnection("jdbc:derby://myhost:1527/db;ssl=peerAuthentication");

Other server commands
The other server commands (shutdown, ping, sysinfo, runtimeinfo, logconnections, maxthreads, timeslice, trace, tracedirectory) are implemented as clients, and they behave exactly as clients with regards to SSL. The SSL mode is set with the property derby.drda.sslMode or the server command option -ssl.
Example:

    java -jar derbyrun.jar server shutdown -ssl basic

will shutdown an SSL-enabled server.
Example:
Similarly, if you have peerAuthentication on both sides, use the following command:

    java -Djavax.net.ssl.keyStore=clientKeyStore.key \
         -Djavax.net.ssl.keyStorePassword=qwerty \
         -Djavax.net.ssl.trustStore=clientTrustStore.key \
         -Djavax.net.ssl.trustStorePassword=qwerty \
         -jar derbyrun.jar server shutdown -ssl peerAuthentication

Configuring the Network Server to handle connections
You can configure the Network Server to use a specific number of threads to handle connections. You can change the configuration on the command line or by using the servlet interface.
The minimum number of threads is the number of threads that are started when the Network Server is booted. This value is specified as a property, derby.drda.minThreads = <min>. The maximum number of threads is the maximum number of threads that will be used for connections. If more connections are active than there are threads available, the extra connections must wait until the next thread becomes available. Threads can become available after a specified time, which is checked only when a thread has finished processing a communication.

• |  | You can change the maximum number of threads by using the following command:
    java org.apache.derby.drda.NetworkServerControl maxthreads <max> [-h <hostname>]
    [-p <portnumber>]
You can also use the derby.drda.maxThreads property to assign the maximum value. A <max> value of 0 means that there is no maximum and a new thread will be generated for a connection if there are no current threads available. This is the default. The <max> and <min> values are stored as integers, so the theoretical maximum is 2147483647 (the maximum size of an integer). But the practical maximum is determined by the machine configuration.
• |  | To change the time that a thread should work on one session's request and check if there are waiting sessions, use the following command:
    java org.apache.derby.drda.NetworkServerControl
    timeslice <milliseconds> [-h <hostname>] [-p <portnumber>]
You can also use the derby.drda.timeSlice property to set this value. A value of 0 milliseconds indicates that the thread will not give up working on the session until the session ends. A value of -1 milliseconds indicates to use the default. The default value is 0. The maximum number of milliseconds that can be specified is 2147483647 (the maximum size of an integer).

Controlling logging by using the log file
The Network Server uses the derby.log file to log problems that it encounters. It also logs connections when the property derby.drda.logConnections is set to true. The derby.log file is created when the Derby server is started. The Network Server then records the time and version. If a log file exists, it is overwritten, unless the property derby.infolog.append is set to true.
When the Network Server is logging connections, it also logs the Connection Number; this log message is written both to the derby.log file and to the Network Server console.

• |  | To turn on connection logging, you can use the servlet interface or you can issue the following command:
    java org.apache.derby.drda.NetworkServerControl
       logconnections on [-h <hostname>] [-p <portnumber>]
• |  | To turn connection logging off you can use the servlet interface or you can issue the following command:
    java org.apache.derby.drda.NetworkServerControl
       logconnections off [-h <hostname>][-p <portnumber>]

See the Java DB Developer's Guide for more information about the derby.log file.
Controlling tracing by using the trace facility
Use the trace facility only if you are working with technical support and they require tracing information.
See Managing the Derby Network Server remotely by using the servlet interface for information about managing the trace facility using the servlet interface.
Turning on the trace facility

1. |  | Turn on tracing for all sessions by specifying the following property:
    derby.drda.traceAll=true
Alternatively, while the Network Server is running, you can use the following command to turn on the trace facility:
    java org.apache.derby.drda.NetworkServerControl
       trace on [-s <connection number>] [-h <hostname>][-p <portnumber>]
If you specify a <connection number>, tracing will be turned on only for that connection.
2. |  | Set the location of the tracing files by specifying the following property:
    derby.drda.traceDirectory=<directory for tracing files>
Alternatively, while the Network Server is running, enter the following command to set the trace directory:
    java org.apache.derby.drda.NetworkServerControl traceDirectory
    <directory for tracing files> [-h <hostname>] [-p <portnumber>]
You need to specify only the directory where the tracing files will reside. The names of the tracing files are determined by the system. If you do not set a trace directory, the tracing files will be placed in derby.system.home. The Network Server will attempt to create the trace directory (and any parent directories) if they do not exist. This will require that the Java security policy for derbynet.jar permits verification of the existence of the named trace directory and all necessary parent directories. For each directory created, the policy must allow
        permission java.io.FilePermission "<directory>", "read,write";
and for the trace directory itself, the policy must allow
        permission java.io.FilePermission "<tracedirectory>${/}-", "write";
See Customizing the Network Server's security policy for information about customizing the Network Server's security policy.

Turning off the trace facility
Enter the following command to turn off tracing:

    java org.apache.derby.drda.NetworkServerControl trace off [-s <connection number>]
    [-h <hostname>] [-p <portnumber>]

The tracing files are named ServerX.trace, where X is a connection number.
Derby Network Server sample programs
This section describes several Derby Network Server sample programs for Network Server users.
The NsSample sample program
The NsSample demonstration program is a simple JDBC application that interacts with the Network Server.
The NsSample program performs the following tasks:

• |  | Starts the Network Server.
• |  | Checks that the Network Server is running.
• |  | Loads the Network Client driver. (Note that this step is not necessary if you are running the client on JDK 1.6 or higher. In that environment, the network client driver loads automatically.)
• |  | Creates the NsSampledb database if not already created.
• |  | Checks to see if the schema is already created, and if not, creates the schema which includes the SAMPLETBL table and corresponding indexes.
• |  | Connects to the database.
• |  | Loads the schema by inserting data.
• |  | Starts client threads to perform database related operations.
• |  | Has each of the clients perform DML operations (select, insert, delete, update) using JDBC calls. For example, one client thread establishes an embedded connection to perform database operations, while another client thread establishes a client connection to the Network Server to perform database operations.
• |  | Waits for the client threads to finish the tasks.
• |  | Shuts down the Network Server at the end of the demonstration.

You must install the following files in the %DERBY_HOME%\demo\nserverdemo\ directory before you can run the sample program:

• |  | NsSample.java This is the entry point into the sample program. The program starts up two client threads. The first client establishes an embedded connection to perform database operations, and the second client establishes a client connection to the Network Server to perform database operations. You can change the following constants to modify the sample program: NUM_ROWS The number of rows that must be initially loaded into the schema. ITERATIONS The number of iterations for which each client thread does database related work. NUM_CLIENT_THREADS The number of clients that you want to run the program against. NETWORKSERVER_PORT The port on which the Network Server is running.
• |  | NsSampleClientThread.java This file contains two Java classes:
• |  | The NsSampleClientThread class extends Thread and instantiates a NsSampleWork instance.
• |  | The NsSampleWork class contains everything that is required to perform DML operations using JDBC calls. The doWork method in the NsSampleWork class represents all the work done as part of this sample program.
• |  | NetworkServerUtil.java This file contains helper methods to start the Network Server and to shutdown the server.

The compiled class files for the NsSample program are:

• |  | NsSample.class
• |  | NsSampleClientThread.class
• |  | NsSampleWork.class
• |  | NetworkServerUtil.class

Running the NsSample sample program
To run the NsSample program:

1. |  | Open a command prompt and change directories to the %DERBY_HOME%\demo\ directory, where %DERBY_HOME% is the directory where you installed Derby.
2. |  | Set the CLASSPATH to the current directory (".") and also include the following jar files in order to use the Network Server and the network client driver: derbynet.jar The Network Server jar file. It must be in your CLASSPATH to use any of the Network Server functions. derbyclient.jar This jar file must be in your CLASSPATH to use the Network Client driver. derby.jar The Derby database engine jar file. derbytools.jar The Derby tools jar file.
3. |  | Test the CLASSPATH settings by running the following Java command:
     java org.apache.derby.tools.sysinfo
This command shows the Derby jar files that are in the classpath as well as their respective versions.
4. |  | After you set up your environment correctly, run the NsSample program from the same directory:
    java nserverdemo.NsSample
If the program runs successfully, you will receive output similar to that shown in the following table:
    Derby Network Server created
    Server is ready to accept connections on port 1621.
    Connection number: 1.
    [NsSample] Derby Network Server started.
    [NsSample] Sample Derby Network Server program demo starting.
    Please wait .....................
    Connection number: 2.
    [NsSampleWork] Begin creating table - SAMPLETBL and necessary indexes.
    [NsSampleClientThread] Thread id - 1; started.
    [NsSampleWork] Thread id - 1; requests database connection,
    	dbUrl =jdbc:derby:NSSampledb;
    [NsSampleClientThread] Thread id - 2; started.
    [NsSampleWork] Thread id - 2; requests database connection,
    	dbUrl =jdbc:derby://localhost:1621/
    	NSSampledb;deferPrepares=true;
    Connection number: 3.
    [NsSampleWork] Thread id - 1 selected 1 row [313,Derby36   ,1.7686243E23,9620]
    [NsSampleWork] Thread id - 1 selected 1 row [313,Derby36   ,1.7686243E23,9620]
    [NsSampleWork] Thread id - 1; deleted 1 row with t_key = 9620
    [NsSampleWork] Thread id - 1 selected 1 row [700,Derby34   ,8.7620301E9,9547]
    [NsSampleWork] Thread id - 1 selected 1 row [700,Derby34   ,8.7620301E9,9547]
    [NsSampleWork] Thread id - 2 selected 1 row [700,Derby34   ,8.7620301E9,9547]
    [NsSampleWork] Thread id - 2 selected 1 row [700,Derby34   ,8.7620301E9,9547]
    [NsSampleWork] Thread id - 1; inserted 1 row.
    [NsSampleWork] Thread id - 1 selected 1 row [52,Derby34   ,8.7620301E9,9547]
    [NsSampleWork] Thread id - 2; updated 1 row with t_key = 9547
    [NsSampleWork] Thread id - 1; deleted 1 row with t_key = 9547
    [NsSampleWork] Thread id - 2 selected 1 row [617,Derby31   ,773.83636,9321]
    [NsSampleWork] Thread id - 2 selected 1 row [617,Derby31   ,773.83636,9321]
    [NsSampleWork] Thread id - 2 selected 1 row [617,Derby31   ,773.83636,9321]
    [NsSampleWork] Thread id - 2 selected 1 row [617,Derby31   ,773.83636,9321]
    [NsSampleWork] Thread id - 1; inserted 1 row.
    [NsSampleWork] Thread id - 2; deleted 1 row with t_key = 9321
    [NsSampleWork] Thread id - 1; deleted 1 row with t_key = 8707
    [NsSampleWork] Thread id - 1; closed connection to the database.
    [NsSampleClientThread] Thread id - 1; finished all tasks.
    [NsSampleWork] Thread id - 2; deleted 1 row with t_key = 8490
    [NsSampleWork] Thread id - 2; closed connection to the database.
    [NsSampleClientThread] Thread id - 2; finished all tasks.
    [NsSample] Shutting down Network Server.
    Connection number: 4.
    Shutdown successful.

Running the NsSample program also creates the following new directories and files:
NSSampledb
This directory makes up the NSSampledb database.
derby.log
This log file contains Derby progress and error messages.
Network Server sample programs for embedded and client connections
This Derby Network Server sample program demonstrates how to obtain an embedded connection and client connections to the same database by using the Network Server. This program shows how to use either the DriverManager or a DataSource to obtain client connections.
For a database to be consistent, only one JVM can access it at a time. The embedded driver is loaded when the Network Server is started. The JVM that starts the Network Server can obtain an embedded connection to the same database that the Network Server is accessing to serve clients from other JVMs. This solution provides the performance benefits of the embedded driver and also allows client connections from other JVMs to connect to the same database.
Overview of the SimpleNetworkServerSample program
The SimpleNetworkServerSample program starts the Derby Network Server, as well as the embedded driver, and waits for clients to connect. The program performs the following tasks.

• |  | Starts the Derby Network Server by using a property and also loads the embedded driver
• |  | Determines if the Network Server is running
• |  | Creates the NSSimpleDB database if it is not already created
• |  | Obtains an embedded database connection
• |  | Tests the database connection by executing a sample query
• |  | Allows client connections to connect to the server until you decide to stop the server and exit the program
• |  | Closes the connection
• |  | Shuts down the Network Server before exiting the program

To run the sample program, install the following files in the %DERBY_HOME%\demo\nserverdemo\ directory:

• |  | The source file: SimpleNetworkServerSample.java
• |  | The compiled class file: SimpleNetworkServerSample.class

Running the SimpleNetworkServerSample program
To run the Derby Network Server sample program:

1. |  | Open a command prompt and change directories to the %DERBY_HOME%\demo\nserverdemo directory, where %DERBY_HOME% is the directory where you installed Derby.
2. |  | Set the classpath to include the current directory ("."), and the following jar files: derbynet.jar The Network Server jar file. It must be in your CLASSPATH because you start the Network Server in this program. derby.jar The database engine jar file. derbytools.jar The Derby tools jar file.
3. |  | Test the CLASSPATH settings by running the following Java command:
    java org.apache.derby.tools.sysinfo
This command displays the Derby jar files that are in the classpath.
4. |  | After you set up your environment correctly, run the SimpleNetworkServerSample program from the same directory:
    java SimpleNetworkServerSample
If the program runs successfully, you will receive output that is similar to that shown in the following exampleS:
    Starting Network Server
    Testing if Network Server is up and running!
    Derby Network Server now running
    Got an embedded connection.
    Testing embedded connection by executing a sample query
    number of rows in sys.systables = 16
    While my app is busy with embedded work, ij might connect like this:

            $ java -Dij.user=me -Dij.password=pw -Dij.protocol=
    			jdbc:derby:\\localhost:1527\ org.apache.derby.tools.ij
            ij> connect 'NSSimpleDB';

    Clients can continue to connect:
    Press [Enter] to stop Server

Running the SimpleNetworkServerSample program also creates the following new directories and files:
NSSimpleDB
This directory makes up the NSSimpleDB database.
derby.log
This log file contains Derby progress and error messages.
Connecting a client to the Network Server with the SimpleNetworkClientSample program
The SimpleNetworkClientSample program is a client program that interacts with the Derby Network Server from another JVM. The program performs the following tasks:

• |  | Loads the network client driver. (Note that this step is not necessary if you are running the client on JDK 1.6 or higher. In that environment, the network client driver loads automatically.)
• |  | Obtains a client connection by using the DriverManager.
• |  | Obtains a client connection by using a DataSource.
• |  | Tests the database connections by running a sample query.
• |  | Closes the connections and then exits the program.

You must install the following files in the %DERBY_HOME%\demo\nserverdemo\ directory before you can run the sample program:

• |  | The source file: SimpleNetworkClientSample.java.
• |  | The compiled class file: SimpleNetworkClientSample.class.

Running the SimpleNetworkClientSample program
To connect to the Network Server that has been started with the SimpleNetworkServerSample program:

1. |  | Open a command prompt and change directories to the%DERBY_HOME%\demo\nserverdemo directory, where %DERBY_HOME% is the directory where you installed Derby.
2. |  | Set the classpath to include the following jar files:
• |  | The current directory (".")
• |  | derbyclient.jar
3. |  | After you set up your environment correctly, run the SimpleNetworkClientSample program from the same directory:
    java SimpleNetworkClientSample
If the program runs successfully, you will receive output similar to that shown in the following example:
    Starting Sample client program
    Got a client connection via the DriverManager.
    connection from datasource;
    Got a client connection via a DataSource.
    Testing the connection obtained via DriverManager by executing a sample query
    number of rows in sys.systables = 16
    Testing the connection obtained via a DataSource by executing a sample query
    number of rows in sys.systables = 16
    Goodbye!

Part two: Derby Administration Guide
This section of the guide is divided into several administrative tasks.
Checking database consistency
If you experience hardware or operating system failure, you can use the SYSCS_UTIL.SYSCS_CHECK_TABLE function to verify that the database is still consistent.
Check consistency only if there are indications that such a check is needed because a consistency check can take a long time on a large database.
The SYSCS_CHECK_TABLE function
The SYSCS_UTIL.SYSCS_CHECK_TABLE() function checks the consistency of a Derby table. In particular, the SYSCS_UTIL.SYSCS_CHECK_TABLE function verifies the following conditions:

• |  | Base tables are internally consistent
• |  | Base tables and all associated indexes contain the same number of rows
• |  | The values and row locations in each index match those of the base table
• |  | All BTREE indexes are internally consistent

You run this function in an SQL statement, as follows:

    VALUES SYSCS_UTIL.SYSCS_CHECK_TABLE(
        SchemaName, TableName)

where SchemaName and TableName are expressions that evaluate to a string data type. If you created a schema or table name as a non-delimited identifier, you must present their names in all upper case. For example:

    VALUES SYSCS_UTIL.SYSCS_CHECK_TABLE('APP', 'CITIES')

The SYSCS_UTIL.SYSCS_CHECK_TABLE function returns a smallint. If the table is consistent (or if you run SYSCS_UTIL.SYSCS_CHECK_TABLE on a view), SYSCS_UTIL.SYSCS_CHECK_TABLE returns a non-zero value. Otherwise, the function throws an exception on the first inconsistency that it finds.
For a consistent table, the following result is displayed:

    1
    -----
    1

    1 row selected

Sample SYSCS_CHECK_TABLE error messages
This section provides examples of error messages that the SYSCS_UTIL.SYSCS_CHECK_TABLE() function can return.
If the row counts of the base table and an index differ, error message X0Y55 is issued:

    ERROR X0Y55: The number of rows in the base table does not match
    the number of rows in at least 1 of the indexes on the table. Index
    'T1_I' on table 'APP.T1' has 4 rows, but the base table has 5 rows.
    The suggested corrective action is to recreate the index.

If the index refers to a row that does not exist in the base table, error message X0X62 is issued:

    ERROR X0X62: Inconsistency found between table 'APP.T1' and index
    'T1_I'. Error when trying to retrieve row location '(1,6)' from the
    table. The full index key,including the row location, is '{ 1, (1,6) }'.
    The suggested corrective action is to recreate the index.

If a key column value differs between the base table and the index, error message X0X61 is issued:

    ERROR X0X61: The values for column 'C10' in index 'T1_C10' and
    table 'APP.T1' do not match for row location (1,7). The value in the
    index is '2 2   ', while the value in the base table is 'NULL'. The full
    index key, including the row location, is '{ 2 2       , (1,7) }'. The
    suggested corrective action is to recreate the index.

Sample SYSCS_CHECK_TABLE queries
This section provides examples that illustrate how to use the SYSCS_UTIL.SYSCS_CHECK_TABLE function in queries.
To check the consistency of a single table, run a query that is similar to the one shown in the following example:

    VALUES SYSCS_UTIL.SYSCS_CHECK_TABLE('APP', 'FLIGHTS')

To check the consistency of all of the tables in a schema, stopping at the first failure, run a query that is similar to the one shown in the following example:

    SELECT tablename, SYSCS_UTIL.SYSCS_CHECK_TABLE(
        'SAMP', tablename)
    FROM sys.sysschemas s, sys.systables t
    WHERE s.schemaname = 'SAMP' AND s.schemaid = t.schemaid

To check the consistency of an entire database, stopping at the first failure, run a query that is similar to the one shown in the following example::

    SELECT schemaname, tablename,
    SYSCS_UTIL.SYSCS_CHECK_TABLE(schemaname, tablename)
    FROM sys.sysschemas s, sys.systables t
    WHERE s.schemaid = t.schemaid

Backing up and restoring databases
Derby provides a way to back up a database while it is online. You can also restore a full backup from a specified location.
Backing up a database
The topics in this section describe how to back up a database.
Offline backups
To perform an offline backup of a database, use operating system commands to copy the database directory. You must shut down the database prior to performing an offline backup.
For example, on Windows systems, the following operating system command backs up a (closed) database that is named sample and that is located in d:\mydatabases by copying it to the directory c:\mybackups\2005-06-01:

    xcopy d:\mydatabases\sample c:\mybackups\2005-06-01\sample /s /i

If you are not using Windows, substitute the appropriate operating system command for copying a directory and all contents to a new location.
Note: On Windows systems, do not attempt to update a database while it is being backed up in this way. Attempting to update a database during an offline backup will generate a java.io.IOException. Using online backups prevents this from occurring.
For large systems, shutting down the database might not be convenient. To back up a database without having to shut it down, you can use an online backup.
Online backups
Use online backups to back up a database while it is running, without blocking transactions.
You can perform online backups by using several types of backup procedures or by using operating systems commands with the freeze and unfreeze system procedures.
Using the backup procedure to perform an online backup:
Use the SYSCS_UTIL.SYSCS_BACKUP_DATABASE procedure to perform an online backup of a database to a specified location.
The SYSCS_UTIL.SYSCS_BACKUP_DATABASE procedure takes a string argument that represents the location in which to back up the database. Typically, you provide the full path to the backup directory. (Relative paths are interpreted as relative to the current directory, not to the derby.system.home directory.)
For example, to specify a backup location of c:/mybackups/2005-06-01 for a database that is currently open, use the following statement (forward slashes are used as path separators in SQL commands):

    CALL SYSCS_UTIL.SYSCS_BACKUP_DATABASE('c:/mybackups/2005-06-01')

The SYSCS_UTIL.SYSCS_BACKUP_DATABASE procedure puts the database into a state in which it can be safely copied. The procedure then copies the entire original database directory (including data files, online transaction log files, and jar files) to the specified backup directory. Files that are not within the original database directory (for example, derby.properties) are not copied. With the exception of a few cases mentioned in Unlogged Operations, the procedure does not block concurrent transactions at any time.
The following example shows how to back up a database to a directory with a name that reflects the current date:

    public static void backUpDatabase(Connection conn)throws SQLException
    {
    // Get today's date as a string:
    java.text.SimpleDateFormat todaysDate =
       new java.text.SimpleDateFormat("yyyy-MM-dd");
    String backupdirectory = "c:/mybackups/" +
       todaysDate.format((java.util.Calendar.getInstance()).getTime());

    CallableStatement cs = conn.prepareCall("CALL SYSCS_UTIL.SYSCS_BACKUP_DATABASE(?)");
    cs.setString(1, backupdirectory);
    cs.execute();
    cs.close();
    System.out.println("backed up database to "+backupdirectory);
    }

For a database that was backed up on 2005-06-01, the previous commands copy the current database to a directory of the same name in c:/mybackups/2005-06-01.
Uncommitted transactions do not appear in the backed-up database.
Note: Do not back up different databases with the same name to the same backup directory. If a database of the same name already exists in the backup directory, it is assumed to be an older version and is overwritten.
Unlogged Operations
For some operations, Derby does not log because it can keep the database consistent without logging the data.
The SYSCS_UTIL.SYSCS_BACKUP_DATABASE procedure will issue an error if there are any unlogged operations in the same transaction as the backup procedure.
If any unlogged operations are in progress in other transactions in the system when the backup starts, this procedure will block until those transactions are complete before performing the backup.
Derby automatically converts unlogged operations to logged mode if they are started while the backup is in progress (except operations that maintain application jar files in the database). Procedures to install, replace, and remove jar files in a database are blocked while the backup is in progress.
If you do not want backup to block until unlogged operations in other transactions are complete, use the SYSCS_UTIL.SYSCS_BACKUP_DATABASE_NOWAIT procedure. This procedure issues an error immediately at the start of the backup if there are any transactions in progress with unlogged operations, instead of waiting for those transactions to complete.
Unlogged operations include:

1. |  | Index creation. Only CREATE INDEX is logged, not all the data inserts into the index. The reason inserts into the index are not logged is: if there is a failure , it will just drop the index. If you create an index when the backup is in progress, it will be slower because it has to be logged. Foreign Keys , Primary Keys create backing indexes. Adding those keys to an existing table with data will also run slower.
2. |  | Import to an empty table or replacing all the data in a table. In this case also, data inserts into table are not logged. Internally, Derby creates a new table for the import and changes the catalogs to point to the new table and drops the original table when import completes. If you perform such an import operation when backup is in progress , it will be slower because data is logged.

Using operating system commands with the freeze and unfreeze system procedures to perform an online backup:
Typically, these procedures are used to speed up the copy operation involved in an online backup. In this scenario, Derby does not perform the copy operation for you. You use the SYSCS_UTIL.SYSCS_FREEZE_DATABASE procedure to lock the database, and then you explicitly copy the database directory by using operating system commands.
For example, because the UNIX tar command uses operating system file-copying routines, and the SYSCS_UTIL.SYSCS_BACKUP_DATABASE procedure uses java I/O calls with additional internal synchronization that allow updates during the backup, the tar command might provide faster backups than the SYSCS_UTIL.SYSCS_BACKUP_DATABASE procedure.
To use operating system commands for online database backups, call the SYSCS_UTIL.SYSCS_FREEZE_DATABASE system procedure. The SYSCS_UTIL.SYSCS_FREEZE_DATABASE system procedure puts the database into a state in which it can be safely copied. After the database has been copied, use the SYSCS_UTIL.SYSCS_UNFREEZE_DATABASE system procedure to continue working with the database. Only after SYSCS_UTIL.SYSCS_UNFREEZE_DATABASE has been specified can transactions once again write to the database. Read operations can proceed while the database is "frozen."
Note: To ensure a consistent backup of the database, Derby might block applications that attempt to write to a frozen database until the backup is completed and the SYSCS_UTIL.SYSCS_UNFREEZE_DATABASE system procedure is called.
The following example demonstrates how the freeze and unfreeze procedures are used to surround an operating system copy command:

    public static void backUpDatabaseWithFreeze(Connection conn)
    	throws SQLException
    {
    Statement s = conn.createStatement();
    s.executeUpdate(
        "CALL SYSCS_UTIL.SYSCS_FREEZE_DATABASE()");
    //copy the database directory during this interval
    s.executeUpdate(
        "CALL SYSCS_UTIL.SYSCS_UNFREEZE_DATABASE()");
    s.close();
    }

When the log is in a non-default location
Note: Read Logging on a separate device to find out about the default location of the database log.
If you put the database log in a non-default location prior to backing up the database, be aware of the following requirements:

• |  | If you are using an operating system command to back up the database, you must explicitly copy the log file as well, as shown in the following example:
    xcopy d:\mydatabases\sample c:\mybackups\2005-06-01\sample /s /i
    xcopy h:\janet\tourslog\log c:\mybackups\2005-06-01\sample\log /s /i

If you are not using Windows, substitute the appropriate operating system command for copying a directory and all of its contents to a new location.

• |  | Edit the logDevice entry in service.properties of the database backup so that it points to the correct location for the log. In the previous example, the log was moved to the default location for a log, so you can remove the logDevice entry entirely, or leave the logDevice entry as is and wait until the database is restored to edit the entry.

See Logging on a separate device for information about putting the log in a non-default location.
Backing up encrypted databases
When you back up an encrypted database, both the backup and the log files remain encrypted.
To restore an encrypted database, you must know the boot password.
Restoring a database from a backup copy
To restore a database by using a full backup from a specified location, specify the restoreFrom=Path attribute in the boot time connection URL.
If a database with the same name exists in the derby.system.home location, the system will delete the database, copy it from the backup location, and then restart it.
The log files are copied to the same location they were in when the backup was taken. You can use the logDevice attribute in conjunction with the restoreFrom=Path attribute to store logs in a different location.
For example, to restore the sample database by using a backup copy in c:\mybackups\sample, the connection URL should be:

    jdbc:derby:sample;restoreFrom=c:\mybackups\sample

For more information, see "restoreFrom=path attribute" in the Java DB Reference Manual.
Creating a database from a backup copy
To create a database from a full backup copy at a specified location, specify the createFrom=Path attribute in the boot time connection URL.
If there is already a database with the same name in derby.system.home, an error will occur and the existing database will be left intact. If there is not an existing database with the same name in the current derby.system.home location, the system will copy the whole database from the backup location to derby.system.home and start it.
The log files are also copied to the default location. You can use the logDevice attribute in conjunction with the createFrom=Path attribute to store logs in a different location. With the createFrom=Path attribute, you do not need to copy the individual log files to the log directory.
For example, to create the sample database from a backup copy in c:\mybackups\sample, the connection URL should be:

    jdbc:derby:sample;createFrom=c:\mybackups\sample

For more information, see "createFrom=path attribute" in the Java DB Reference Manual.
Roll-forward recovery
Derby supports roll-forward recovery to restore a damaged database to the most recent state before a failure occurred.
Derby restores a database from full backup and replays all the transactions after the backup. All the log files after a backup are required to replay the transactions after the backup. By default, the database keeps only logs that are required for crash-recovery. For roll-forward recovery to be successful, all log files must be archived after a backup. Log files can be archived using the backup function calls that enable log archiving.
In roll-forward recovery the log archival mode ensures that all old log files are available. The log files are available only from the time that the log archival mode is enabled.
Derby uses the following information to restore the database:

• |  | The backup copy of the database
• |  | The set of archived logs
• |  | The current online active log

You cannot use roll-forward recovery to restore individual tables. Roll-forward recovery recovers the entire database.
To restore a database by using roll-forward recovery, you must already have a backup copy of the database, all the archived logs since the backup was created, and the active log files. All the log files should be in the database log directory.
There are two types of log files in Derby: active logs and online archived logs.
Active logs
Active logs are used during crash recovery to prevent a failure that might leave a database in an inconsistent state. Roll-forward recovery can also use the active logs to recover to the end of the log files. Active logs are located in the database log path directory.
Online archived logs
Log files that are stored for roll-forward recovery use when they are no longer needed for crash recovery. Online archived logs are also kept in the database log path directory.
Enabling log archival mode
Online archive logs are available only if the database is enabled for log archival mode. You can use the following system procedure to enable the database for log archival mode:

    SYSCS_UTIL.SYSCS_BACKUP_DATABASE_AND_ENABLE_LOG_ARCHIVE_MODE
    (IN BACKUPDIR VARCHAR(32672), IN SMALLINT DELETE_ARCHIVED_LOG_FILES)

The input parameters for the calls in the previous example specify the location where the backup should be stored and specify whether or not the database should keep online archived logs for the backup. Existing online archived log files that were created before this backup will be deleted if the input parameter value for the deleteOnlineArchivedLogFiles parameter is non-zero. The log files are deleted only after a successful backup.
Note: Make sure to store the backup database in a safe place when you choose the log file removal option.
The SYSCS_UTIL.SYSCS_BACKUP_DATABASE_AND_ENABLE_LOG_ARCHIVE_MODE procedure will issue an error if there are any unlogged operations in the same transaction as backup procedure.
If any unlogged operations are in progress in other transactions in the system when the backup starts, this procedure will block until those transactions are complete before performing the backup. Derby automatically converts unlogged operations to logged mode if they are started while the backup is in progress (except operations that maintain application jar files in the database). Procedures to install, replace, and remove jar files in a database are blocked while the backup is in progress.
If you do not want backup to block until unlogged operations in other transactions are complete, use the SYSCS_UTIL.SYSCS_BACKUP_DATABASE_AND_ENABLE_LOG_ARCHIVE_MODE_NOWAIT procedure. This procedure issues an error immediately at the start of the backup if there are any transactions in progress with unlogged operations, instead of waiting for those transactions to complete.
Disabling log archival mode:
After you enable log archival mode, the database will always have the log archival mode enabled even if it is subsequently booted or backed up. The only way to disable the log archive mode is to run the following procedure:

    SYSCS_UTIL.SYSCS_DISABLE_LOG_ARCHIVE_MODE(IN SMALLINT DELETE_ARCHIVED_LOG_FILES)

This system procedure disables the log archive mode and deletes any existing online archived log files if the input parameter DELETE_ARCHIVED_LOG_FILES is non-zero.
Performing roll-forward recovery:
By using the full backup copy, archived logs, and active logs, you can restore a database to its most recent state by performing roll-forward recovery. You perform a roll-forward recovery by specifying the connection URL attribute rollForwardRecoveryFrom=path at boot time. This brings the database to its most recent state by using full backup copy, archived logs, and active logs. All the log files should be in the database log path directory.
For more information, see "rollForwardRecoveryFrom=path attribute" in the Java DB Reference Manual.
Backing up a database:
In the following example, a database named wombat is backed up to the d:/backup directory with log archive mode enabled:

    connect 'jdbc:derby:wombat;create=true';

    create table t1(a int not null primary key);
    ------------------DML/DDL Operations
    CALL SYSCS_UTIL.SYSCS_BACKUP_DATABASE_AND_ENABLE_LOG_ARCHIVE_MODE
    ('d:/backup', 0);
    insert into t1 values(19);
    create table t2(a int);
    -----------------DML/DDL Operations
    -----------------Database Crashed (Media Corruption on data disks)

Restoring a database using roll-forward recovery:
In the following example, the database is restored using roll-forward recovery after a media failure:

    connect 'jdbc:derby:wombat;rollForwardRecoveryFrom=d:/backup/wombat';
    select * from t1;
    ---------------DML/DDL Operations

After a database is restored from full backup, transactions from the online archived logs and active logs are replayed.
Replicating databases
Replication is an important feature of a robust database management system. In Derby, you start database replication by using connection URL attributes.
The replication capability of Derby has the following features:

• |  | One master, one slave: A replicated database resides in two locations and is managed by two different Derby instances. One of these Derby instances has the master role for this database, and the other has the slave role. Typically, the master and slave run on different nodes, but this is not a requirement. Together, the master and its associated slave represent a replication pair.
• |  | Roll-forward shipped log: Replication is based on shipping the Derby transaction log from the master to the slave, and then rolling forward the operations described in the log to the slave database.
• |  | Asymmetry: Only the master processes transactions. The slave processes no transactions, not even read operations.
• |  | Asynchronicity: Transactions are committed on the master without waiting for the slave. The shipping of the transaction log to the slave is performed regularly, and is completely decoupled from the transaction execution at the master. This may lead to a few lost transactions if the master crashes.
• |  | Shared nothing: Apart from the network line, no hardware is assumed to be shared.
• |  | Replication granularity: The granularity for replication is exactly one database. However, one Derby instance may have different roles for different databases. For example, one Derby instance may have the following roles, all at the same time:
• |  | The master role for one database D1 replicated to one node
• |  | The slave role for a database D2 replicated from another node
• |  | The normal, non-replicated, role for a database D3

Replication builds on Derby's ability to recover from a crash by starting with a backup and rolling forward Derby's transaction log files. The master sends log records to the slave using a network connection. The slave then writes these log records to its local log and redoes them.
If the master fails, the slave completes the recovery by redoing the log that has not already been processed. The state of the slave after this recovery is close to the state the master had when it crashed. However, some of the last transactions performed on the master may not have been sent to the slave and may therefore not be reflected. When the slave has completed the recovery work, it is transformed into a normal Derby instance that is ready to process transactions. For more details, see Forcing a failover and Replication and security.
Several Derby properties allow you to specify the size of the replication log buffers and the intervals between log shipments, as well as whether replication messages are logged. See the Java DB Reference Manual for details.
You can perform replication on a database that runs in either embedded mode or Network Server mode.
Starting and running replication
Each replicated database is replicated from a master to a slave version of that database. Initially there is no replication; a master database must be created before it can be replicated. The database may, of course, be empty when replication starts. On the other hand, replication does not need to be specified immediately after the database is created; it can be initiated at any time after the database is created.
Before you start replication, you must shut down the master database and then copy the database to the slave location. Follow these steps to start replication:

1. |  | Make sure that the database on the master system is shut down cleanly.
2. |  | Copy the database to the slave location.
3. |  | Start slave replication mode on the Derby instance that is acting as the slave for the database. To start slave replication, use the startSlave=true attribute and, optionally, the slaveHost=hostname and slavePort=portValue attributes. For example, for a database named wombat, you might use the following connection URL:
    jdbc:derby:wombat;startSlave=true
4. |  | Start master replication mode on the Derby instance that is acting as the master for the database. To start replication, connect to the database on the master system using the startMaster=true attribute in conjunction with the slaveHost=hostname attribute (and, optionally, the slavePort=portValue attribute). For example, you might use the following connection URL:
    jdbc:derby:wombat;startMaster=true;slaveHost=myremotesystem
A successful use of the startMaster=true attribute will also start the database.

See the Java DB Reference Manual for details about these attributes.
After replication has been started, the slave is ready to receive logged operations from the master. The master can now continue to process transactions. From this point on, the master forwards all logged operations to the slave in chunks. The slave repeats these operations by applying the contents of the Derby transaction log, but does not process any other operations. Attempts to connect to the slave database are refused. In case of failure, the slave can recover to the state the master was in at the time the last chunk of the transaction log was sent.
While replication is running, neither the slave or the master database is permitted to be shut down. Replication must be stopped before you can shut down either the slave or the master database. There is one exception to this rule: if the entire system is shut down, the peer that is shut down notifies the other replication peer that replication is stopped.
If you install jar files on the master system while replication is running, the same jars are not automatically installed on the slave. But because the transaction log information sent to the slave system includes the jar file installation, the slave database has a record of the jar files, even though they are not actually there. Therefore, you must install the jar files on the former slave after a failover by calling either SQLJ.remove_jar followed by SQLJ.install_jar, or SQLJ.replace_jar. (For information on installing jar files, see "Storing jar files in a database" in the Java DB Tools and Utilities Guide.)
If the jar files must be available to clients immediately after a failover, you must stop replication and then start replication over again from the beginning, so that the slave database will have the same jar files as the master.
Stopping replication
To stop replication of a database, connect to the master database using the stopMaster=true connection URL attribute. The master sends the remaining log records that await shipment, and then sends a stop replication command to the slave. The slave then writes all logs to disk and shuts down the database. For example, for a database named wombat, you might specify the following connection URL:

    jdbc:derby:wombat;stopMaster=true

To stop replication on the slave system if the connection to the master is lost, use the stopSlave=true connection URL attribute.
See the Java DB Reference Manual for details about these attributes.
You cannot resume replication after it has been stopped. You need to start replication over again from the beginning using the startMaster=true attribute, as described in Starting and running replication.
Forcing a failover
At any time, you can transform the Derby database that has the slave role into a normal Derby database that can process transactions. This transformation from being a slave to becoming an active Derby database is called failover. During failover, the slave applies the parts of the transaction log that have not yet been processed. It then undoes operations that belong to uncommitted transactions, resulting in a transaction-consistent state that includes all transactions whose commit log record has been sent to the slave.
You perform failover from the master system. To do so, you connect to the database on the master system using the failover=true connection URL attribute. For example, for a database named wombat, you might specify the following connection URL:

    jdbc:derby:wombat;failover=true

If the network connection between the master system and the slave system is lost, you can perform failover from the slave system.
See the Java DB Reference Manual for details about the failover=true attribute.
There is no automatic failover or restart of replication after one of the instances has failed.
Replication and security
If you want to perform replication with the security manager enabled, you must modify the security policy file on both the master and slave systems to allow the master-slave network connection. The section to be modified is the one following this line:

    grant codeBase "${derby.install.url}derby.jar"

Add the following permission to the policy file on the master system:

      permission java.net.SocketPermission "slaveHost:slavePort", "connect,resolve";

Add the following permission to the policy file on the slave system:

      permission java.net.SocketPermission "slaveHost", "accept,resolve";

slaveHost and slavePort are the values you specify for the slaveHost=hostname and slavePort=portValue attributes, which are described in the Java DB Reference Manual.
See Basic Network Server security policy for details on the security policy file.
Depending on the security mode Derby is running under, the measures described in the following table are enforced when you specify the replication-related connection URL attributes.
Table 7. Replication behavior with Derby security

Security mode | Replication attribute requirements
No security | Anyone may specify the replication attributes
Authentication is turned on | Normal Derby connection policy: specify valid user=userName and password=userPassword attributes
Authorization is turned on | The user=userName and password=userPassword attributes must be valid, and the user must be the owner of the replicated database

Replication failure handling
Replication can encounter several failure situations. The following table lists these situations and describes the actions that Derby takes as a result.
Table 8. Replication failure handling

Failure situation | Action taken
Master loses connection with slave. | Transactions are allowed to continue processing while the master tries to reconnect with the slave. Log records generated while the connection is down are buffered in main memory. If the log buffer reaches its size limit before the connection can be reestablished, the master replication functionality is stopped. You can use the property derby.replication.logBufferSize to configure the size limit of the buffer; see the Java DB Reference Manual for details.
Slave loses connection with master. | The slave tries to reestablish the connection with the master by listening on the specified host and port. It will not give up until it is explicitly requested to do so by either the failover=true or stopSlave=true connection URL attribute. If a failover is requested, the slave applies all received log records and boots the database as described in Forcing a failover. If the stopSlave=true attribute is specified, the slave database is shut down without further actions.
Two different masters of database D try to replicate to the same slave. | The slave will only accept the connection from the first master attempting to connect. Note that authentication is required to start both the slave and the master, as described in Replication and security.
The master and slave Derby instances are not at the same Derby version. | An exception is raised and replication does not start.
The master Derby instance crashes, then restarts. | Replication must be restarted, as described in Starting and running replication.
The master Derby instance is not able to send log data to the slave at the same pace as the log is generated. The main memory log buffer gradually fills up and eventually becomes full. | The master notices that the main memory log buffer is filling up. It first tries to increase the speed of the log shipment to keep the amount of log in the buffer below the maximum. If that is not enough to keep the buffer from getting full, the response time of transactions may increase for as long as log shipment has trouble keeping up with the amount of generated log records. You can use properties to tune both the log buffer size and the minimum and maximum interval between consecutive log shipments. See the Java DB Reference Manual for details.
The slave Derby instance crashes. | The master sees this as a lost connection to the slave. The master tries to reestablish the connection until the replication log buffer is full. Replication is then stopped on the master. Replication must be restarted, as described in Starting and running replication.
An unexpected failure is encountered. | Replication is stopped. The other Derby instance of the replication pair is notified of the decision if the network connection is still alive.

Logging on a separate device
You can improve the performance of update-intensive, large databases by putting a database's log on a separate device, which reduces I/O contention.
By default, the transaction log is in the log subdirectory of the database directory. Use either of the following methods to store this log subdirectory in another location:

• |  | Specify the non-default location by using the logDevice=logDirectoryPath attribute on the database connection URL when you create the database.
• |  | If the database is already created, move the log manually and update the service.properties file.

Using the logDevice=logDirectoryPath attribute
To specify a non-default location for the log directory, set the logDevice=logDirectoryPath attribute on the database connection URL when you create the database.
This attribute is meaningful only when you are creating a database. You can specify logDevice=logDirectoryPath as either an absolute path or as a path that is relative to the directory where the JVM is executed.
Setting logDevice=logDirectoryPath on the database connection URL adds an entry to the service.properties file. If you ever move the log manually, you will need to alter the entry in service.properties. If you move the log back to the default location, remove the logDevice entry from the service.properties file.
To check the log location for an existing database, you can retrieve the logDevice=logDirectoryPath attribute as a database property by using the following statement:

    VALUES SYSCS_UTIL.SYSCS_GET_DATABASE_PROPERTY('logDevice')

For more information, see "logDevice=logDirectoryPath attribute" in the Java DB Reference Manual.
Example of creating a log in a non-default location
The following database connection URL creates a database in the directory d:/mydatabases, but puts the database log directory in h:/janets/tourslog:

    jdbc:derby:d:/mydatabases/toursDB;
        create=true;logDevice=h:/janets/tourslog

Example of moving a log manually
If you want to move the log to g:/bigdisk/tourslog, move the log with operating system commands:

    move h:\janets\tourslog\log\*.* g:\bigdisk\tourslog\log

Then, alter the logDevice entry in service.properties to read as follows:

    logDevice=g:/bigdisk/toursLog

Note: You can use either a single forward slash or double back slashes for a path separator.
If you later want to move the log back to its default location (in this case, d:\mydatabases\toursDB\log), move the log manually as follows:

    move g:\bigdisk\tourslog\log\*.* d:\mydatabases\toursDB\log

Then, delete the logDevice entry from service.properties.
Note: This example uses commands that are specific to the Windows NT operating system. Use commands appropriate to your operating system to copy a directory and all of its contents to a new location.
Issues for logging in a non-default location
When the log is not in the default location, backing up and restoring a database can require extra steps. See Backing up and restoring databases for details.
Obtaining locking information
Derby provides a tool to monitor and display locking information. This tool can help you create applications that minimize deadlock. It can also help you locate the cause of deadlock when it does occur.
To diagnose locking problems, constantly monitor locking traffic by logging all deadlocks by using the derby.locks.monitor property.
Monitoring deadlocks
The derby.stream.error.logSeverityLevel property determines the level of error that you are informed about.
By default, derby.stream.error.logSeverityLevel is set to 40000. If derby.stream.error.logSeverityLevel is set to display transaction-level errors (that is, if it is set to a value less than 40000), deadlock errors are logged to the derby.log file. If it is set to a value of 40000 or higher, deadlock errors are not logged to the derby.log file.
The derby.locks.monitor property ensures that deadlock errors are logged regardless of the value of derby.stream.error.logSeverityLevel. When derby.locks.monitor is set to true, all locks that are involved in deadlocks are written to derby.log along with a unique number that identifies the lock.
To see a thread's stack trace when a lock is requested, set derby.locks.deadlockTrace to true. This property is ignored if derby.locks.monitor is set to false.
Note: Use derby.locks.deadlockTrace with care. Setting this property can alter the timing of the application, severely affect performance, and produce a very large derby.log file.
For information about working with properties, see the Java DB Developer's Guide. For information about the specific properties that are mentioned in this topic, see the Java DB Reference Manual.
Here is an example of an error message when Derby aborts a transaction because of a deadlock:

    --SQLException Caught--

    SQLState: 40001 =
    Error Code: 30000
    Message: A lock could not be obtained due to a deadlock,
    cycle of locks and waiters is: Lock : ROW, DEPARTMENT, (1,14)
    Waiting XID : {752, X} , APP, update department set location='Boise'
    	where deptno='E21'
    Granted XID : {758, X} Lock : ROW, EMPLOYEE, (2,8)
    Waiting XID : {758, U} , APP, update employee set bonus=150 where salary=23840
    Granted XID : {752, X} The selected victim is XID : 752

Note: You can use the derby.locks.waitTimeout and derby.locks.deadlockTimeout properties to configure how long Derby waits for a lock to be released, or when to begin deadlock checking. For more information about these properties, see the section that discusses controlling Derby application behavior in the Java DB Developer's Guide.
Reclaiming unused space
A Derby table or index (sometimes called a conglomerate) can contain unused space after large amounts of data have been deleted or updated.
This happens because, by default, Derby does not return unused space to the operating system. After a page has been allocated to a table or index, Derby does not automatically return the page to the operating system until the table or index is dropped, even if the space is no longer needed. However, Derby does provide a way to reclaim unused space in tables and associated indexes.
If you determine that a table and its indexes have a significant amount of unused space, use either the SYSCS_UTIL.SYSCS_COMPRESS_TABLE or SYSCS_UTIL.SYSCS_INPLACE_COMPRESS_TABLE procedure to reclaim that space. SYSCS_COMPRESS_TABLE is guaranteed to recover the maximum amount of free space, at the cost of temporarily creating new tables and indexes before the statement is committed. SYSCS_INPLACE_COMPRESS attempts to reclaim space within the same table, but cannot guarantee it will recover all available space. The difference between the two procedures is that unlike SYSCS_COMPRESS_TABLE, the SYSCS_INPLACE_COMPRESS procedure uses no temporary files and moves rows around within the same conglomerate.
You can use the SYSCS_DIAG.SPACE_TABLE diagnostic table to estimate the amount of unused space in a table or index by examining, in particular, the values of the NUMFREEPAGES and ESTIMSPACESAVING columns. For example:

    SELECT * FROM TABLE(SYSCS_DIAG.SPACE_TABLE('APP', 'FLIGHTAVAILABILITY')) AS T

For more information about SYSCS_DIAG.SPACE_TABLE, see "SYSCS_DIAG diagnostic tables and functions" in the Java DB Reference Manual.
As an example, after you have determined that the FlightAvailability table and its related indexes have too much unused space, you could reclaim that space with the following command:

    call SYSCS_UTIL.SYSCS_COMPRESS_TABLE('APP', 'FLIGHTAVAILABILITY', 0);

The third parameter in the SYSCS_UTIL.SYSCS_COMPRESS_TABLE() procedure determines whether the operation will run in sequential or non-sequential mode. If you specify 0 for the third argument in the procedure, the operation will run in non-sequential mode. In sequential mode,Derby compresses the table and indexes sequentially, one at a time. Sequential compression uses less memory and disk space but is slower. To force the operation to run in sequential mode, substitute a non-zero SMALLINT value for the third argument. The following example shows how to force the procedure to run in sequential mode:

    call SYSCS_UTIL.SYSCS_COMPRESS_TABLE('APP', 'FLIGHTAVAILABILITY', 1);

For more information about this command, see the Java DB Reference Manual.
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