IBM SDK and Runtime Environment for Linux platforms, Java 2 Technology Edition, Version 5.0

User Guide


Copyright information

Note: Before using this information and the product it supports, be sure to read the general information under Notices.

This edition of the User Guide applies to the:

and to all subsequent releases and modifications until otherwise indicated in new editions.

(c) Copyright Sun Microsystems, Inc. 1997, 2004, 901 San Antonio Rd., Palo Alto, CA 94303 USA. All rights reserved.

(c) Copyright International Business Machines Corporation, 1999, 2007. All rights reserved.

U.S. Government Users Restricted Rights - Use, duplication or disclosure restricted by GSA ADP Schedule Contract with IBM Corp.

Preface

This User Guide provides general information about the IBM(R) SDK and Runtime Environment for Linux(TM) platforms, Java(TM) 2 Technology Edition, Version 5.0 and specific information about any differences in the IBM implementation compared with the Sun implementation. Read this User Guide in conjunction with the more extensive documentation on the Sun Web site: http://java.sun.com.

For the list of distributions against which the SDK and Runtime Environment for Linux have been tested, see: http://www-106.ibm.com/developerworks/java/jdk/linux/tested.html.

The Diagnostics Guide provides more detailed information about the IBM Virtual Machine for Java.

The terms "Runtime Environment" and "Java Virtual Machine" are used interchangeably throughout this User Guide.

Technical changes made to this User Guide for Version 5.0, other than minor or obvious ones such as updating "1.4.2" to "5.0", are indicated in red when viewing in HTML or in a color-printed copy and by vertical bars to the left of the changes.

Contents

Copyright information
Preface
Overview
Conventions
Version compatibility
Upgrading the SDK
Migrating from other IBM JVMs
| |
Supported hardware for zSeries
Contents of the SDK and Runtime Environment
Runtime Environment tools
SDK tools
Installing and configuring the SDK and Runtime Environment
Installing on Red Hat Enterprise Linux (RHEL) 4 or 5
| |
Running Java with SELinux on RHEL 5
| |
Installing a 32-bit SDK on 64-bit architecture
Installing from an RPM file
Installing from a .tgz file
| |
Using a JPackage compatible format
Configuring the SDK and Runtime Environment for Linux
Setting the PATH
Setting the CLASSPATH
Uninstalling the SDK and Runtime Environment for Linux
Uninstalling the Red Hat Package Manager (RPM) package
Uninstalling the compressed Tape Archive (TAR) package
Using the Runtime Environment
Options
Specifying Java options and system properties
Standard options
Nonstandard options
Obtaining the IBM build and version number
Globalization of the java command
The Just-In-Time (JIT) compiler
Disabling the JIT
Enabling the JIT
Determining whether the JIT is enabled
Specifying garbage collection policy
Garbage collection options
Pause time
Pause time reduction
Environments with very full heaps
How the JVM processes signals
Signals used by the JVM
Linking a native code driver to the signal-chaining library
Working with floating stacks
Transforming XML documents
Using an older version of Xerces or Xalan
Using the SDK to develop Java applications
Debugging Java applications
Java Debugger (JDB)
Determining whether your application is running on a 32-bit or 64-bit JVM
Writing JNI applications
| |
Support for thread-level recovery of blocked connectors
Working with applets
Running applets with the Applet Viewer
Debugging applets with the Applet Viewer
| |
Configuring large page memory allocation
CORBA support
Support for GIOP 1.2
Support for Portable Interceptors
Support for Interoperable Naming Service
System properties for tracing the ORB
System properties for tuning the ORB
Java 2 security permissions for the ORB
ORB implementation classes
RMI over IIOP
Implementing the Connection Handler Pool for RMI
Enhanced BigDecimal
Euro symbol support
| |
Fallback font configuration files
Using the Java Communications API (JavaComm)
Installing Java Communications API
Location of Java Communications API files
Configuring Java Communications API
Changing the access mode of serial and parallel ports
Enabling serial ports on IBM ThinkPads
Printing limitation with the Java Communications API
Uninstalling Java Communications API
Uninstalling the installable Red Hat Package Manager (RPM) package
Uninstalling the compressed Tape Archive (TAR) package
Java Communications API documentation
Deploying Java applications
(Linux IA 32-bit and PPC32 only) Using the Java Plug-in
Supported browsers
Installing and configuring the Java Plug-in
Common Document Object Model (DOM) support
Using DBCS parameters
(Linux IA 32-bit, PPC32, and PPC64 only) Using Web Start
Running Web Start
| |
(Linux IA 32-bit only) Secure Static Versioning support
Shipping Java applications
| |
Class data sharing between JVMs
| |
Overview of class sharing
| |
Cache contents
| |
Dynamic updating of the cache
| |
Enabling class sharing
| |
Cache security
| |
Cache lifespan
| |
Cache utilities
| |
Using command-line options for class sharing
| |
Creating, populating, monitoring, and deleting a cache
| |
Performance and memory consumption
| |
Limitations and considerations of using class sharing
| |
Cache size limits
| |
Runtime bytecode modification
| |
Operating system limitations
| |
Using SharedClassPermission
| |
Adapting custom classloaders to share classes
Service and support for independent software vendors
Accessibility
iKeyman accessibility
Keyboard traversal of JComboBox components in Swing
(Linux IA 32-bit, PPC32, and PPC64 only) Web Start accessibility
Known limitations
Limitations that apply to all Linux platforms except where indicated
Linux IA 32-bit limitations
Linux AMD64 limitations
Linux PPC 32-bit and 64-bit limitations
Linux PPC 64-bit limitations
Linux zSeries 64-bit limitations
Linux zSeries 31-bit and 64-bit limitations
Any comments on this User Guide?
Notices
Trademarks

Overview

The IBM SDK is a development environment for writing and running applets and applications that conform to the Java 5.0 Core Application Program Interface (API).

The SDK includes the Runtime Environment for Linux, which enables you only to run Java applications. If you have installed the SDK, the Runtime Environment is included.

The Runtime Environment contains the Java Virtual Machine and supporting files including non-debuggable .so files and class files. The Runtime Environment contains only a subset of the classes that are found in the SDK and allows you to support a Java program at runtime but does not allow you to compile Java programs. The Runtime Environment for Linux does not include any of the development tools, such as appletviewer or the Java compiler (javac), or classes that are only for development systems.

In addition, for IA32, PPC32, and AMD64/EM64T platforms, the Java Communications application programming interface (API) package is provided for use with the Runtime Environment for Linux. You can find information about it in Using the Java Communications API (JavaComm).

The license_xx.html file contains the license agreement for the Runtime Environment for Linux software. (xx is an abbreviation for the language.) To view or print the license agreement, open the file in a Web browser.

Conventions

Throughout this User Guide the default installation directory of the SDK is referred to as /opt/ibm/java2-i386-50/. The platforms listed below have different default installation directories; replace the directory for the platform you are using when you see /opt/ibm/java2-i386-50/:

Version compatibility

In general, any applet or application that ran with a previous version of the SDK should run correctly with the IBM SDK for Linux, v5.0. Classes compiled with this release are not guaranteed to work on previous releases.

To read Sun's documentation on compatibility, see the Sun Web site at http://java.sun.com.

Upgrading the SDK

If you are upgrading the SDK from a previous release, back up all the configuration files and security policy files before you start the upgrade.

After the upgrade, you might have to restore or reconfigure these files because they might have been overwritten during the upgrade process. Check the syntax of the new files before restoring the original files because the format or options for the files might have changed.

Migrating from other IBM JVMs

From Version 1.4.2 for AMD64/EM64T and Version 5 for the other Linux platforms, the IBM Runtime Environment for Linux contains new versions of the IBM Virtual Machine for Java and the Just-In-Time (JIT) compiler. If you are migrating from an older IBM Runtime Environment, note that:

| | |

Supported hardware for zSeries

|

The zSeries 31-bit and |64-bit SDKs and Runtime Environments run on the following |System z9 and zSeries servers or equivalents:

|

Contents of the SDK and Runtime Environment

The SDK contains several development tools and a Java Runtime Environment (JRE). This section describes the contents of the SDK tools and the Runtime Environment.

Applications written entirely in Java should have no dependencies on the IBM SDK's directory structure (or files in those directories). Any dependency on the SDK's directory structure (or the files in those directories) could result in application portability problems.

Runtime Environment tools

SDK tools

Note: The User Guides, Javadoc, and the accompanying license, copyright files, javadoc, and demo directory are the only documentation included in this SDK for Linux. You can view Sun's software documentation by visiting the Sun Web site, or you can download Sun's software documentation package from the Sun Web site: http://java.sun.com.

Installing and configuring the SDK and Runtime Environment

You can install the IBM Java SDK and Runtime Environment from either an RPM or a .tgz file. Unless you want to allow all the users on the machine to access this Java installation, use .tgz installation method. If you do not have root access, use the .tgz file.

If you install using an RPM file, the Java files are installed in /opt/ibm/java2-i386-50/. The examples in this guide assume that you have installed Java in this directory.

|Installing on Red Hat Enterprise Linux (RHEL) 4 or |5

For RHEL 4 and 5, the SDK depends on shared libraries that are not installed by default.

In RHEL 4, the RPMs that contain these libraries are:

To include these libraries during RHEL 4 installation:

  1. When you reach the Package Defaults screen, select Customize the set of packages to be installed.
  2. At the Package Group Selection screen, under X Windows System, choose Details and make sure that you have selected xorg-x11-deprecated-libs.
  3. Under the Development options, select Legacy Software Development.

In RHEL 5, the RPMs that contain these libraries are:

|To include these libraries during RHEL 5 installation:

    | |
  1. At the software selection screen, select Customize now.
  2. |
  3. On the next screen, in the left-hand panel, select Base System; in the right-hand panel, select Legacy Software Support. These selections will install the compat-libstdc++ |packages.
  4. |
  5. The libXp package is required but is not available to select for installation |from the install GUI. When installation is complete, open a shell, locate |the libXp package on your Red Hat installation media, and install it. For |example, to install on a 32-bit Intel platform: |
    rpm -i /media/cdrom/Server/libXp-1.0.0-8.i386.rpm
| | |

Running Java with SELinux on RHEL 5

|

To run the IBM SDK for Java on Red Hat Enterprise Linux Version 5 with |SELinux enabled, Java must be installed in the default directory. If Java |is not installed in the default directory, you must disable SELinux or add |SELinux exceptions for Java in the installed location.

|

For more information about SELinux, see http://www.redhat.com/magazine/006apr05/features/selinux/

| | |

Installing a 32-bit SDK on 64-bit architecture

|

To run the SDK, you must install the correct versions of all libraries |required by the SDK, either 32- or 64-bit.

|

In |RHEL4, the 32-bit versions of the packages are available in the Compatibility Arch Support package group.

|

You can use the RPM tool to check which versions of the packages you have |installed by adding the option --queryformat "%{NAME}.%{ARCH}\n" to |your RPM command. For example:

|
/home/username : rpm --queryformat "%{NAME}.%{ARCH}\n" -q libstdc++
|libstdc++.x86_64
|libstdc++.i386

Installing from an RPM file

|To upgrade your JVM using the rpm tool, |you must uninstall any previous version. To install two versions of the JVM |in different locations, use the rpm --force option to ignore the |version conflict or install the JVM from the .tgz file.

To install from an RPM file:

  1. Open a shell prompt, making sure you are root.
  2. At a shell prompt, type rpm -ivh <RPM file>. For example:
    |rpm -ivh ibm-java2-<arch>-sdk-5.0-0.0.<arch>.rpm
    or
    |rpm -ivh ibm-java2-<arch>-jre-5.0-0.0.<arch>.rpm

    |Where <arch> represents your architecture: |i386, x86_64, ppc, ppc64, s390, or s390x.

Installing from a .tgz file

To install from a .tgz file:

  1. Create a directory to store the Java package files. The examples in this guide assume that you have installed in /opt/ibm/java2-i386-50/. In the rest of the guide, replace /opt/ibm/java2-i386-50/ with the directory in which you installed Java.
  2. At a shell prompt, type tar -zxvf <.tgz file>. For example:
    |tar -zxvf ibm-java2-sdk-50-linux-<arch>.tgz
    or
    |tar -zxvf ibm-java2-jre-50-linux-<arch>.tgz

    |Where <arch> represents your architecture: i386, x86_64, ppc, |ppc64, s390, or s390x.

| | |

Using a JPackage compatible format

|

From Version 5.0 Service Refresh 3, the IBM Java package is also available |in a JPackage compatible format. To simplify managing the SDK, the various |components of it are now available as separate RPMs: the base Java Runtime |Environment, Development Kit, Plug-in, JDBC, Demo, Sound, Source, and |Fonts. "jpackage-utils" RPM (downloadable from http://jpackage.org), which allows managing multiple Java RPMs on a system, is a prerequisite |for the IBM SDKs as well. For more information on the JPackage specification, |see http://jpackage.org

Configuring the SDK and Runtime Environment for Linux

Setting the PATH

Note that, if you alter the PATH environment variable as described below, you will override any existing Java executables in your path.

After setting the path, you can run a tool by typing its name at a shell prompt with a filename as an argument.

You can specify the path to a tool by typing the path before the name of the tool each time. For example, if the SDK is installed in /opt/ibm/java2-i386-50/bin, you can compile a file named myfile.java by typing the following at a shell prompt:

  /opt/ibm/java2-i386-50/bin/javac myfile.java

To change the PATH environment variable:

  1. Edit the shell startup file in your home directory (usually .bashrc, depending on your shell) and add the absolute paths to the PATH environment variable; for example:
    export PATH=/opt/ibm/java2-i386-50/bin:/opt/ibm/java2-i386-50/jre/bin:$PATH

  2. Log on again or run the updated shell script to activate the new PATH setting.

Setting the CLASSPATH

The CLASSPATH tells the SDK tools, such as java, javac, and javadoc, where to find the Java class libraries.

You need to set the CLASSPATH explicitly only if one of the following applies:

To display the current value of your CLASSPATH, type the following at a shell prompt:

  echo $CLASSPATH

If you develop and run applications that use different runtime environments, including other versions that you have installed separately, you must set the CLASSPATH (and PATH) explicitly for each application. If you run multiple applications simultaneously and use different runtime environments, each application must run in its own shell.

If you run only one version of Java at a time, you can use a shell script to switch between the different runtime environments.


Note:
(For Linux IA 32-bit Chinese users only) Because of inconsistencies in the font encodings on Red Hat Advanced Server, when you install for an environment in which you want Chinese to be the default language, it is better to install with a default language of English and then change to Chinese after the installation is complete. Otherwise, you might find that the Chinese fonts do not display.

Uninstalling the SDK and Runtime Environment for Linux

The process that you use to remove the SDK and Runtime Environment for Linux depends on what type of installation you used. See Uninstalling the Red Hat Package Manager (RPM) package or Uninstalling the compressed Tape Archive (TAR) package for instructions.

Uninstalling the Red Hat Package Manager (RPM) package

To uninstall the SDK or Runtime Environment for Linux if you installed the installable RPM package:

  1. At a shell prompt,
    1. To check which RPM packages you have installed, type:
      rpm -qa | grep -i java
    2. You will see a list of any IBM Java packages that you have installed; for example:
      ibm-java2-<arch>-jre-5.0-0.0.<arch>
      ibm-java2-<arch>-sdk-5.0-0.0.<arch>
      
    3. This output tells you which packages you can uninstall, using the rpm -e command; for example:
      rpm -e ibm-java2-<arch>-jre-5.0-0.0.<arch>
      rpm -e ibm-java2-<arch>-sdk-5.0-0.0.<arch>
    Alternatively, you can use a graphical tool such as kpackage or yast2
  2. Remove from your PATH statement the directory in which you installed the SDK and Runtime Environment.
  3. (Linux IA 32-bit and PPC32 only) If you installed the Java Plug-in, remove the Java Plug-in files from the web browser directory.

Uninstalling the compressed Tape Archive (TAR) package

To uninstall the SDK or Runtime Environment for Linux if you extracted the compressed TAR package:

  1. Remove the SDK or Runtime Environment files from the directory in which you installed the SDK or Runtime Environment.
  2. Remove from your PATH statement the directory in which you installed the SDK or Runtime Environment.
  3. Log on again or run the updated shell script to activate the new PATH setting.
  4. (Linux IA 32-bit and AMD64/EM64T only) If you installed the Java Plug-in, remove the Java Plug-in files from the web browser directory.

Using the Runtime Environment

The java tool launches a Java application by starting a Java Runtime Environment and loading a specified class.

The JVM searches for the initial class (and other classes that are used) in three sets of locations: the bootstrap classpath, the installed extensions, and the user classpath. The arguments that you specify after the class name or JAR file name are passed to the main function.

The javaw command is identical to java, except that javaw has no associated console window. Use javaw when you do not want a command prompt window to appear. The javaw launcher displays a dialog box with error information if a launch fails.

The java and javaw command have the following syntax:

java [ options ] class [ arguments ... ]
java [ options ] -jar file.jar [ arguments ... ]
javaw [ options ] class [ arguments ... ]
javaw [ options ] -jar file.jar [ arguments ... ]

Items that are within brackets are optional.

options
Command-line options.
class
Name of the class to invoke.
file.jar
Name of the jar file to invoke. It is used only with -jar.
arguments
Arguments passed to the main function.

If the -jar option is specified, the named JAR file must contain class and resource files for the application, with the startup class indicated by the Main-Class manifest header.

Options

The launcher has a set of standard options that are supported on the current runtime environment and will be supported in future releases. In addition, there is a set of nonstandard options. The default options have been chosen for best general use. Plan carefully before making changes.

Specifying Java options and system properties

You can specify Java options and system properties in these ways. In order of precedence, they are:

  1. By specifying the option or property on the command line. For example, java -Dmysysprop1=tcpip -Dmysysprop2=wait -Xdisablejavadump MyJavaClass.
  2. By creating a file that contains the options, and specifying it on the command line using -Xoptionsfile=<filename>.
  3. By creating an environment variable called IBM_JAVA_OPTIONS containing the options. For example:
    export IBM_JAVA_OPTIONS="-Dmysysprop1=tcpip -Dmysysprop2=wait -Xdisablejavadump"

Rightmost options on the command line have precedence over leftmost options; for example, if you specify the options -Xint -Xjit myClass, -Xjit takes precedence.

Standard options

Nonstandard options

The -X options listed below are nonstandard and subject to change without notice.

For options that take <size> parameter, you should suffix the number with "k" or "K" to indicate kilobytes, "m" or "M" to indicate megabytes, or "g" or "G" to indicate gigabytes.

Obtaining the IBM build and version number

To obtain the IBM build and version number, at a shell prompt type:

java -version

Globalization of the java command

The java command and other java launcher commands (such as javaw) allow a class name to be specified as any character that is in the character set of the current locale.

You can also specify any Unicode character in the class name and arguments by using Java escape sequences. To do this, you must specify -Xargencoding. To specify a Unicode character, use escape sequences in the form \u####, where # is a hexadecimal digit (0 through 9, A through F).

Alternatively, to specify that the class name and command arguments are in UTF8 encoding, use -Xargencoding:utf8, or in ISO8859_1 encoding use -Xargencoding:latin.

For instance, to specify a class called "HelloWorld" using Unicode encoding for both capital letters, use this command:

java -Xargencoding '\u0048ello\u0057orld'

The java and javaw commands give translated output messages. These messages differ based on the locale in which Java is running. The detailed error descriptions and other debug information that is returned by java are in English.

The Just-In-Time (JIT) compiler

The IBM Just-In-Time (JIT) compiler dynamically generates machine code for frequently used bytecode sequences in Java applications and applets during their execution. |The JIT V5.0 compiler delivers new optimizations |as a result of compiler research, improves optimizations implemented in previous |versions of the JIT, and provides better hardware exploitation.

The IBM SDK and Runtime Environment include the JIT, which is enabled by default in user applications as well as SDK tools. Normally, there is no need to invoke the JIT explicitly; the compilation of Java bytecode to machine code occurs transparently. However, if you encounter a problem with the Runtime Environment while executing a Java application or an applet, you can disable the JIT to help isolate the problem. Disabling the JIT should be a temporary measure only; the JIT is required for adequate performance.

Disabling the JIT

There are three ways to disable the JIT:

Both command-line options override the JAVA_COMPILER environment variable.

Enabling the JIT

To enable the JIT explicitly, set the JAVA_COMPILER environment variable to "jitc", or use the -D option to set the java.compiler property to "jitc". Alternatively, use the -Xjit option (and omit the -Xint option) on the JVM command line to turn on the JIT.

If the JAVA_COMPILER environment variable or the java.compiler property is set to "" (the empty string), the JIT remains disabled. To unset the environment variable properly, type unset JAVA_COMPILER at the shell prompt.

Determining whether the JIT is enabled

To determine whether the JIT is enabled, type the following at a command prompt:

java -version

If the JIT is not in use, a message is displayed that includes the following:

(JIT disabled)

If the JIT is in use, a message is displayed that includes the following:

(JIT enabled)

For more information about the JIT, see the Diagnostics Guide.

Specifying garbage collection policy

The Garbage Collector manages the memory used by Java and by applications running within the VM.

When the Garbage Collector receives a request for storage, unused memory in the heap is set aside - "allocation". The Garbage Collector also checks for areas of memory are no longer referenced, and releases them for reuse - "collection".

The collection phase can be triggered by a memory allocation fault, which occurs when no space is left for a storage request, or by an explicit System.gc() call.

Garbage collection can significantly affect application performance, so the IBM virtual machine provides various methods of optimising the way garbage collection is carried out, thus reducing the effect on your application.

For more detailed information on garbage collection, see the Diagnostics Guide.

Garbage collection options

The -Xgcpolicy option controls garbage collector behavior, making tradeoffs between throughput of the application and overall system and the pause times that are caused by garbage collection.

The format of the option and its values is:

Pause time

When an application's attempt to create an object cannot be satisfied immediately from the available space in the heap, the garbage collector is responsible for identifying unreferenced objects (garbage), deleting them, and returning the heap to a state in which the immediate and subsequent allocation requests can be satisfied quickly. Such garbage collection cycles introduce occasional unexpected pauses in the execution of application code. Because applications grow in size and complexity, and heaps become correspondingly larger, this garbage collection pause time tends to grow in size and significance. The default garbage collection value, -Xgcpolicy:optthruput, delivers very high throughput to applications, but at the cost of these occasional pauses, which can vary from a few milliseconds to many seconds, depending on the size of the heap and the quantity of garbage.

Pause time reduction

The JVM uses two techniques to reduce pause times:

The -Xgcpolicy:optavgpause command-line option requests the use of concurrent garbage collection to reduce significantly the time that is spent in garbage collection pauses. Concurrent GC reduces the pause time by performing some garbage collection activities concurrently with normal program execution to minimize the disruption caused by the collection of the heap. The -Xgcpolicy:optavgpause option also limits the effect of increasing the heap size on the length of the garbage collection pause. The -Xgcpolicy:optavgpause option is most useful for configurations that have large heaps. With the reduced pause time, you might experience some reduction of throughput to your applications.

During concurrent garbage collection a significant amount of time is wasted identifying relatively long-lasting objects that cannot then be collected. If the GC concentrates on just those objects that are most likely to be recyclable, you can further reduce pause times for some applications. Generational GC achieves this by dividing the heap into two "generations", the "nursery" and the "tenure" areas. Objects are placed in one of these areas depending on their age. The nursery is the smaller of the two and contains younger objects; the tenure is larger and contains older objects. Objects are first allocated to the nursery; if they survive long enough they are promoted to the tenure area eventually.

Generational GC depends on most objects not lasting long. Generational GC reduces pause times by concentrating the effort to reclaim storage on the nursery because it has the most recyclable space. Rather than occasional but lengthy pause times to collect the entire heap, the nursery is collected more frequently and, if the nursery is small enough, pause times are comparatively short. However, generational GC has the drawback that, over time, the tenure area might become full if too many objects last too long. To minimize the pause time when this situation occurs, use a combination of concurrent GC and generational GC. The -Xgcpolicy:gencon option requests the combined use of concurrent and generational GC to help minimize the time that is spent in any garbage collection pause.

Environments with very full heaps

If the Java heap becomes nearly full, and very little garbage is to be reclaimed, requests for new objects might not be satisfied quickly because no space is immediately available. If the heap is operated at near-full capacity, application performance might suffer regardless of which of the above options is used; and, if requests for more heap space continue to be made, the application receives an OutOfMemoryError, which results in JVM termination if the exception is not caught and handled. At this point the JVM produces a "javadump" diagnostic file. In these conditions, you are recommended either to increase the heap size by using the -Xmx option, or to reduce the number of application objects in use. For more information, see the Diagnostics Guide.

How the JVM processes signals

When a signal is raised that is of interest to the JVM, a signal handler is called. This signal handler determines whether it has been called for a Java or non-Java thread.

If the signal is for a Java thread, the JVM takes control of the signal handling. If an application handler for this signal is installed and you did not specify the -Xnosigchain command-line option, the application handler for this signal is called after the JVM has finished processing.

If the signal is for a non-Java thread, and the application that installed the JVM had previously installed its own handler for the signal, control is given to that handler. Otherwise, if the signal is requested by the JVM or Java application, the signal is ignored or the default action is taken.

For exception and error signals, the JVM either:

For information about writing a launcher that specifies the above hooks, see: http://www-106.ibm.com/developerworks/java/library/i-signalhandling/. This item was written for Java V1.3.1, but still applies to later versions.

For interrupt signals, the JVM also enters a controlled shutdown sequence, but this time it is treated as a normal termination that:

The shutdown is identical to the shutdown initiated by a call to the Java method System.exit().

Other signals that are used by the JVM are for internal control purposes and do not cause it to terminate. The only control signal of interest is SIGQUIT, which causes a Javadump to be generated.

Signals used by the JVM

Table 1 below shows the signals that are used by the JVM. The signals are grouped in the table by type or use, as follows:

Table 1. Signals used by the JVM
Signal Name Signal type Description Disabled by -Xrs
SIGBUS (7) Exception Incorrect access to memory (data misalignment) Yes
SIGSEGV (11) Exception Incorrect access to memory (write to inaccessible memory) Yes
SIGILL (4) Exception Illegal instruction (attempt to invoke an unknown machine instruction) No
SIGFPE (8) Exception Floating point exception (divide by zero) Yes
SIGABRT Error Abnormal termination. The JVM raises this signal whenever it detects a JVM fault. Yes
SIGINT (2) Interrupt Interactive attention (CTRL-C). JVM exits normally. Yes
SIGTERM (15) Interrupt Termination request. JVM will exit normally. Yes
SIGHUP (1) Interrupt Hang up. JVM exits normally. Yes
SIGQUIT Control A quit signal for a terminal. JVM uses this for taking Javadumps. Yes
|SIGTRAP (5) |Control |Used by the JIT. |Yes
|__SIGRTMAX - 2 |Control |Used by the SDK. |No
|SIGCHLD |Control |Used by the SDK for internal control. |No

Use the -Xrs (reduce signal usage) option to prevent the JVM from handling most signals. For more information, see Sun's Java application launcher page.

Signals 1 (SIGHUP), 2 (SIGINT), 4 (SIGILL), 7 (SIGBUS), 8 (SIGFPE), 11 (SIGSEGV), and 15 (SIGTERM) on JVM threads cause the JVM to shut down; therefore, an application signal handler should not attempt to recover from these unless it no longer requires the JVM.

Linking a native code driver to the signal-chaining library

The Runtime Environment contains signal-chaining. Signal-chaining enables the JVM to interoperate more efficiently with native code that installs its own signal handlers.

Signal-chaining enables an application to link and load the shared library libjsig.so before the system libraries. The libjsig.so library ensures that calls such as signal(), sigset(), and sigaction() are intercepted so that their handlers do not replace the JVM's signal handlers. Instead, these calls save the new signal handlers, or "chain" them behind the handlers that are installed by the JVM. Later, when any of these signals are raised and found not to be targeted at the JVM, the preinstalled handlers are invoked.

To use libjsig.so:

If you install signal handlers that use sigaction() , some sa_flags are not observed when the JVM uses the signal. These are:

The libjsig.so library also hides JVM signal handlers from the application. Therefore, calls such as signal(), sigset(), and sigaction() that are made after the JVM has started no longer return a reference to the JVM's signal handler, but instead return any handler that was installed before JVM startup.

Working with floating stacks

Particular Linux distributions - Red Hat, for example - have enabled a GLIBC feature called 'floating stacks'. Because of Linux kernel limitations, the JVM does not run on SMP hardware with floating stacks enabled if the kernel level is less than 2.4.10. In this environment, floating stacks must be disabled before the JVM, or any application that starts the JVM, is started. On Red Hat, use this command to disable floating stacks by exporting an environment variable:

export LD_ASSUME_KERNEL=2.2.5

On a nonfloating stack Linux system, regardless of what is set for -Xss, a minimum native stack size of 256 KB for each thread is provided. On a floating stack Linux system, the -Xss values are honored. Therefore, if you are migrating from a non-floating stack Linux system, you must ensure that any -Xss values are large enough and are not relying on a minimum of 256 KB.

Transforming XML documents

The IBM SDK contains the XSLT4J processor and the XML4J parser that conform to the JAXP 1.3 specification. These tools allow you to parse and transform XML documents independently from any given XML processing implementation. By using "Factory Finders" to locate the SAXParserFactory, DocumentBuilderFactory and TransformerFactory implementations, your application can swap between different implementations without having to change any code.

|The XML technology included with the IBM SDK is similar to |Apache Xerces Java and Apache Xalan Java. See http://xml.apache.org/xerces2-j/ and http://xml.apache.org/xalan-j/ for more information.

The XSLT4J processor allows you to choose between the original XSLT Interpretive processor or the new XSLT Compiling processor. The Interpretive processor is designed for tooling and debugging environments and supports the XSLT extension functions that are not supported by the XSLT Compiling processor. The XSLT Compiling processor is designed for high performance runtime environments; it generates a transformation engine, or translet, from an XSL style sheet. This approach separates the interpretation of style sheet instructions from their runtime application to XML data.

The XSLT Interpretive processor is the default processor. To select the XSLT Compiling processor, you can:

To implement properties in the jaxp.properties file, copy jaxp.properties.sample to jaxp.properties in /opt/ibm/java2-i386-50/jre/lib. This file also contains full details about the procedure used to determine which implementations to use for the TransformerFactory, SAXParserFactory, and the DocumentBuilderFactory.

To improve the performance when you transform a StreamSource object with the XSLT Compiling processor, specify the com.ibm.xslt4j.b2b2dtm.XSLTCB2BDTMManager class as the provider of the service org.apache.xalan.xsltc.dom.XSLTCDTMManager. To determine the service provider, try each step until you find org.apache.xalan.xsltc.dom.XSLTCDTMManager:

  1. Check the setting of the system property org.apache.xalan.xsltc.dom.XSLTCDTMManager.
  2. Check the value of the property org.apache.xalan.xsltc.dom.XSLTCDTMManager in the file /opt/ibm/java2-i386-50/jre/lib/xalan.properties.
  3. Check the contents of the file META-INF/services/org.apache.xalan.xsltc.dom.XSLTCDTMManager for a class name.
  4. Use the default service provider, org.apache.xalan.xsltc.dom.XSLTCDTMManager.

The XSLT Compiling processor detects the service provider for the org.apache.xalan.xsltc.dom.XSLTCDTMManager service when a javax.xml.transform.TransformerFactory object is created. Any javax.xml.transform.Transformer or javax.xml.transform.sax.TransformerHandler objects that are created by using that TransformerFactory object will use the same service provider. You can change service providers by modifying one of the settings described above and then creating a new TransformerFactory object.

Using an older version of Xerces or Xalan

If you are using an older version of Tomcat, this limitation might apply.

If you are using an older version of Xerces (prior to 2.0) or Xalan (prior to 2.3) in the endorsed override, you might get a null pointer exception when you launch your application. This exception occurs because these older versions do not handle the jaxp.properties file correctly.

To avoid this situation, use one of the following workarounds:

Using the SDK to develop Java applications

The following sections give information about using the SDK for Linux to develop Java applications. See SDK tools for details of the tools available.

Debugging Java applications

To debug Java programs, you can use the Java Debugger (JDB) application or other debuggers that communicate by using the Java Platform Debugger Architecture (JPDA) that is provided by the SDK for Linux.

More information on problem diagnosis using Java can be found in the IBM Java Diagnostics Guide.

Java Debugger (JDB)

The Java Debugger (JDB) is included in the SDK for Linux. The debugger is invoked by the jdb command; it "attaches" to the JVM using JPDA. To debug a Java application:

  1. Start the JVM with the following options:
    java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=<port> MyApp <args>
  2. The JVM starts up, but suspends execution before it starts the Java application. In a separate session, you can attach the debugger to the JVM:
    jdb -attach <port number>
    The debugger will attach to the JVM, and you can now issue a range of commands to examine and control the Java application; for example, type run to allow the Java application to execute.

To find out more about JDB options, type:

jdb -help

To find out more about JDB commands:

  1. Type jdb
  2. At the jdb prompt, type help

You can also use JDB to debug Java applications running on remote machines. JPDA uses a TCP/IP socket to connect to the remote JVM.

  1. Start the JVM as before.
  2. Attach the debugger to the remote machine:
    jdb -attach <machine name or IP address>:<port number>

When you launch a debug session using the dt_socket transport, be sure that the specified ports are free to use.

|The Java Virtual Machine Debugging Interface (JVMDI) is not supported in this release. It has been replaced by |the Java Virtual Machine Tool Interface (JVMTI).

For more information on JDB and JPDA and their usage, see these Web sites:


Determining whether your application is running on a 32-bit or 64-bit JVM

Some Java applications must be able to determine whether they are running on a 32-bit JVM or on a 64-bit JVM. For example, if your application has a native code library, the library must be compiled separately in 32- and 64-bit forms for platforms that support both 32- and 64-bit modes of operation. In this case, your application must load the correct library at runtime, because it is not possible to mix 32- and 64-bit code.

The system property com.ibm.vm.bitmode allows applications to determine the mode in which your JVM is running. It returns the following values:

You can inspect the com.ibm.vm.bitmode from within your application code using the call:

System.getProperty("com.ibm.vm.bitmode");

Writing JNI applications

Valid JNI version numbers that native programs can specify on the JNI_CreateJavaVM() API call are:

This version number determines only the level of the JNI native interface to use. The actual level of the JVM that is created is specified by the J2SE libraries (that is, v5.0). The JNI interface API does not affect the language specification that is implemented by the JVM, the class library APIs, or any other area of JVM behavior. For more information, see http://java.sun.com/j2se/1.5.0/docs/guide/jni.

If your application needs two JNI libraries, one built for 32- and the other for 64-bit, use the com.ibm.vm.bitmode system property to determine if you are running with a 32- or 64-bit JVM and choose the appropriate library.

To compile and link a native application with the IBM 5.0 SDK, use the following command:

gcc -I/opt/ibm/java2-i386-50/include -L/opt/ibm/java2-i386-50/jre/bin/j9vm 
-ljvm -ldl -lpthread <JNI program filename>

The -ljvm option specifies that libjvm.so is the shared library that implements the JVM. The -lpthread option indicates that you are using native pthread support; if you do not link with the pthread library, a segmentation fault (signal SIGSEGV) might be caused when you run the JNI program.

Note:
Version 1.1 of the Java Native Interface (JNI) is not supported.
| | |

Support for thread-level recovery of blocked connectors

|

Four new IBM-specific SDK classes have been added to the com.ibm.jvm package |to support the thread-level recovery of blocked connectors. The new classes |are packaged in core.jar.

|

These classes allow you to unblock threads that have become blocked on |networking or synchronisation calls. If an application does not use these |classes, it must end the whole process, rather than interrupting an individual |blocked thread.

|

The classes are:

|
|
public Interface InterruptibleContext()
|
Defines two methods, isblocked() and unblock(). The other three classes |implement InterruptibleContext. |
|
public class InterruptibleLockContext()
|
Is a utility class for interrupting synchronization calls. |
|
public class InterruptibleIOContext()
|
Is a utility class for interrupting network calls. |
|
public class InterruptibleThread()
|
Is a utility class that extends java.lang.Thread, to allow wrapping |of interruptible runnable methods. It uses instances of InterruptibleLockContext |and InterruptibleIOContext to perform the required isblocked() and unblock() |methods depending on whether a synchronization or networking operation is |blocking the thread. |
|
|

Both InterruptibleLockContext and InterruptibleIOContext work by referencing |the current thread. Therefore if you do not use InterruptibleThread, you must |provide your own class that extends java.lang.Thread, to use these new classes.

|

The Javadoc for these classes is provided with the SDK in the file docs/apidoc.zip.

Working with applets

With the Applet Viewer, you can run one or more applets that are called by reference in a Web page (HTML file) by using the APPLET tag. The Applet Viewer finds the APPLET tags in the HTML file and runs the applets, in separate windows, as specified by the tags.

Because the Applet Viewer is for viewing applets, it cannot display a whole Web page that contains many HTML tags. It parses only the APPLET tags and no other HTML on the Web page.

Running applets with the Applet Viewer

To run an applet with the Applet Viewer, type the following at a shell prompt:

   appletviewer name

where name is one of the following:

For example, to invoke the Applet Viewer on an HTML file that calls an applet, type at a shell prompt:

  appletviewer $HOME/filename.html

where filename is the name of the HTML file.

For example, http://java.sun.com/applets/NervousText/example1.html is the URL of a Web page that calls an applet. To invoke the Applet Viewer on this Web page, type at a shell prompt:

appletviewer http://java.sun.com/applets/NervousText/example1.html

The Applet Viewer does not recognize the charset option of the <META> tag. If the file that the Applet Viewer loads is not encoded as the system default, an I/O exception might occur. To avoid the exception, use the -encoding option when you run appletviewer. For example:

appletviewer -encoding JISAutoDetect sample.html

Debugging applets with the Applet Viewer

You can debug applets by using the -debug option of the Applet Viewer. When debugging applets, you are advised to invoke the Applet Viewer from the directory that contains the HTML file that calls the applet. For example:

cd demo/applets/TicTacToe
../../bin/appletviewer -debug example1.html

You can find documentation about how to debug applets using the Applet Viewer at the Sun Web site: http://java.sun.com.

| | |

Configuring large page memory allocation

|

You can enable large page support, on systems that support it, by starting |Java with the -Xlp option.

|

Large page usage is primarily intended to provide performance improvements |to applications that allocate a lot of memory and frequently access that memory. |The large page performance improvements are mainly caused by the reduced number |of misses in the Translation Lookaside Buffer (TLB). The TLB maps a larger |virtual memory range and thus causes this improvement.

|

Large page support must be available in the kernel, and enabled, |to allow Java to use large pages.

|

To configure large page memory allocation, first ensure that |the running kernel supports large pages. Check that the file /proc/meminfo |contains the following lines:

|
HugePages_Total:     <number of pages>
|HugePages_Free:      <number of pages>
|Hugepagesize:        <page size, in kB>

The number of pages available |and their sizes vary between distributions.

|

If large page support is not available in your kernel, these |lines will not exist in the /proc/meminfo file. In this case, you must install |a new kernel containing support for large pages.

|

If large page support is available, but not enabled, HugePages_Total will be 0. In this case, your administrator must enable |large page support. Check your operating system manual for more instructions.

|

For the JVM to use large pages, your system must have an adequate number |of contiguous large pages available. If large pages cannot be allocated, even |when enough pages are available, possibly the large pages are not contiguous. Configuring the number of large pages at bootup will create |them contiguously.

|

Large page allocations will only succeed if the JVM has root |access. To use large pages, either run Java as root or set the suid bit of |the Java executable.

CORBA support

The Java 2 Platform, Standard Edition (J2SE) supports, at a minimum, the specifications that are defined in the Official Specifications for CORBA support in J2SE (V1.5). In some cases, the IBM J2SE ORB supports more recent versions of the specifications.

Support for GIOP 1.2

This SDK supports all versions of GIOP, as defined by chapters 13 and 15 of the CORBA 2.3.1 specification, OMG document formal/99-10-07, which you can obtain from:

http://www.omg.org/cgi-bin/doc?formal/99-10-07

Bidirectional GIOP is not supported.

Support for Portable Interceptors

This SDK supports Portable Interceptors, as defined by the OMG in the document ptc/01-03-04, which you can obtain from:

http://www.omg.org/cgi-bin/doc?ptc/01-03-04

Portable Interceptors are hooks into the ORB through which ORB services can intercept the normal flow of execution of the ORB.

Support for Interoperable Naming Service

This SDK supports the Interoperable Naming Service, as defined by the OMG in the document ptc/00-08-07, which you can obtain from:

http://www.omg.org/cgi-bin/doc?ptc/00-08-07

The default port that is used by the Transient Name Server (the tnameserv command), when no ORBInitialPort parameter is given, has changed from 900 to 2809, which is the port number that is registered with the IANA (Internet Assigned Number Authority) for a CORBA Naming Service. Programs that depend on this default might have to be updated to work with this version.

The initial context that is returned from the Transient Name Server is now an org.omg.CosNaming.NamingContextExt. Existing programs that narrow the reference to a context org.omg.CosNaming.NamingContext still work, and do not need to be recompiled.

The ORB supports the -ORBInitRef and -ORBDefaultInitRef parameters that are defined by the Interoperable Naming Service specification, and the ORB::string_to_object operation now supports the ObjectURL string formats (corbaloc: and corbaname:) that are defined by the Interoperable Naming Service specification.

The OMG specifies a method ORB::register_initial_reference to register a service with the Interoperable Naming Service. However, this method is not available in the Sun Java Core API at Version 5.0. Programs that need to register a service in the current version must invoke this method on the IBM internal ORB implementation class. For example, to register a service "MyService":

((com.ibm.CORBA.iiop.ORB)orb).register_initial_reference("MyService",
serviceRef); 

where orb is an instance of org.omg.CORBA.ORB, which is returned from ORB.init(), and serviceRef is a CORBA Object, which is connected to the ORB. This mechanism is an interim one, and is not compatible with future versions or portable to non-IBM ORBs.

System properties for tracing the ORB

A runtime debug feature provides improved serviceability. You might find it useful for problem diagnosis or it might be requested by IBM service personnel. Tracing is controlled by three system properties.

For example, to trace events and formatted GIOP messages, type:

 java -Dcom.ibm.CORBA.Debug=true  
		-Dcom.ibm.CORBA.CommTrace=true myapp   

Do not turn on tracing for normal operation, because it might cause performance degradation. Even if you have switched off tracing, FFDC (First Failure Data Capture) is still working, so that only serious errors are reported. If a debug output file is generated, examine it to check on the problem. For example, the server might have stopped without performing an ORB.shutdown().

The content and format of the trace output might vary from version to version.

System properties for tuning the ORB

The following properties help you to tune the ORB:

Java 2 security permissions for the ORB

When running with a Java 2 SecurityManager, invocation of some methods in the CORBA API classes might cause permission checks to be made, which might result in a SecurityException. Affected methods include the following:

Table 2. Methods affected when running with Java 2 SecurityManager
Class/Interface Method Required permission
org.omg.CORBA.ORB

init

java.net.SocketPermission resolve

org.omg.CORBA.ORB

connect

java.net.SocketPermission listen

org.omg.CORBA.ORB

resolve_initial_references

java.net.SocketPermission connect

org.omg.CORBA.
portable.ObjectImpl

_is_a

java.net.SocketPermission connect

org.omg.CORBA.
portable.ObjectImpl

_non_existent

java.net.SocketPermission connect

org.omg.CORBA.
portable.ObjectImpl

OutputStream _request (String, boolean)

java.net.SocketPermission connect

org.omg.CORBA.
portable.ObjectImpl

_get_interface_def

java.net.SocketPermission connect

org.omg.CORBA.
Request

invoke

java.net.SocketPermission connect

org.omg.CORBA.
Request

send_deferred

java.net.SocketPermission connect

org.omg.CORBA.
Request

send_oneway

java.net.SocketPermission connect

javax.rmi.
PortableRemoteObject

narrow

java.net.SocketPermission connect

If your program uses any of these methods, ensure that it is granted the necessary permissions.

ORB implementation classes

The ORB implementation classes in this release are:

These are the default values, and you are advised not to set these properties or refer to the implementation classes directly. For portability, make references only to the CORBA API classes, and not to the implementation. These values might be changed in future releases.

RMI over IIOP

Java Remote Method Invocation (RMI) provides a simple mechanism for distributed Java programming. RMI over IIOP (RMI-IIOP) uses the Common Object Request Broker Architecture (CORBA) standard Internet Inter-ORB Protocol (IIOP protocol) to extend the base Java RMI to perform communication. This allows direct interaction with any other CORBA Object Request Brokers (ORBs), whether they were implemented in Java or another programming language.

The following documentation is available:

Implementing the Connection Handler Pool for RMI

Thread pooling for RMI Connection Handlers is not enabled by default.

To enable the connection pooling implemented at the RMI TCPTransport level, set the option

-Dsun.rmi.transport.tcp.connectionPool=true (or any non-null value) 

This version of the Runtime Environment does not have any setting that you can use to limit the number of threads in the connection pool.

For more information, see the Sun Java site: http://java.sun.com.

Enhanced BigDecimal

| |

|From Java 5.0, the IBM BigDecimal class has been adopted |by Sun as java.math.BigDecimal. The com.ibm.math.BigDecimal class is reserved |for possible future use by IBM, and, currently, you are recommended to regard |it as deprecated. You are recommended to migrate existing Java code to use |java.math.BigDecimal.|

|

|The new java.math.BigDecimal uses the same methods as both |the previous java.math.BigDecimal and com.ibm.math.BigDecimal. Existing code |using java.math.BigDecimal continues to work correctly. The two classes do |not serialize.|

|

To migrate existing Java code to use the java.math.BigDecimal class, change |the import statement at the top of your java file from: import com.ibm.math.*; to import java.math.*;.

Euro symbol support

The IBM SDK and Runtime Environment set the Euro as the default currency for those countries in the European Monetary Union (EMU) for dates on or after 1 January, 2002.

To use the old national currency, specify -Duser.variant=PREEURO on the Java command line.

If you are running the UK, Danish, or Swedish locales and want to use the Euro, specify -Duser.variant=EURO on the Java command line.

|In V5.0 SR3, the default for the Slovenian locale is set |to the Euro. If you install SR3 before 1 January 2007, you might want to change |the currency to the Tolar.

| | |

Fallback font configuration files

|

The Linux fallback font configuration files (fontconfig.RedHat.bfc and |fontconfig.SuSE.bfc) are installed from Version 5.0 Service Refresh 4 onwards |to provide font settings suitable for new enterprise Linux distributions that |were being developed when Service Refresh 4 was made available. These files |are for your convenience only. Their presence does not imply that the new |Linux distribution is a supported platform for the IBM SDK and Runtime Environment for Linux platforms, Java 2 Technology Edition, Version 5.0.

Using the Java Communications API (JavaComm)

The Java Communications application programming interface (API) package (JavaComm) is an optional package provided for use with the Runtime Environment for Linux on the IA32, PPC32/PPC64, and AMD64/EM64T platforms. You install JavaComm independently of the SDK or Runtime Environment.

The JavaComm API gives Java applications a platform-independent way of performing serial and parallel port communications for technologies such as voice mail, fax, and smartcards. After writing serial or parallel port communications for your application, you can then include those files with your application.

The Java Communications API supports Electronic Industries Association (EIA)-232 (RS232) serial ports and Institute of Electrical and Electronics Engineers (IEEE) 1284 parallel ports and is supported on systems with the IBM Version 5.0 Runtime Environment.

Using Java Communications API, you can:

Installing Java Communications API

You should make sure that a copy of the SDK or Runtime Environment is installed before you install the Java Communications API.

If you used the RPM package to install Java originally, install the Java Communications API from the RPM file. To install the Java Communications API from an RPM package:

  1. Open a shell prompt, making sure you are root.
  2. Using the rpm -ivh command, install the Java Communications API RPM file. For example:
    rpm -ivh ibm-java2-<arch>-javacomm-5.0-0.0.<arch>.rpm

    The Java Communications API is installed within the /opt/ibm/java2-i386-50/ directory structure.

To install the Java Communications API from a .tgz file:

  1. Put the Java Communications API archive file, ibm-java2-javacomm-50-linux-<arch>.tgz, in the directory containing the IBMJava2-50 directory.
  2. From a shell prompt, in the directory containing the .tgz file, extract the contents:
    tar -xvzf ibm-java2-javacomm-50-linux-<arch>.tgz
    

    The Java Communications API is extracted into subdirectories within the existing IBMJava2-50 directory.

Location of Java Communications API files

The Java Communications API files are installed as shown:

If you installed to the default directory, the comm.jar file is in /opt/ibm/java2-i386-50/jre/lib/ext.

If you installed the package in another directory, the files are in the same directory structure, but /opt/ibm/java2-i386-50/ is replaced by the directory where you installed Java Communications API.

Configuring Java Communications API

After you install Java Communications API, you must:

Changing the access mode of serial and parallel ports

After you install Java Communications API, you must change the access mode of serial and parallel ports so that users can access these devices. You must give a user read/write access to the required devices. Log on as root and use the following commands, as applicable:

    chmod 666 /dev/ttyS0    (also known as serial port COM1) 
    chmod 666 /dev/lp0      (also known as parallel port LPT1)
    chmod 666 /dev/ttyS1    (also known as serial port COM2)
    chmod 666 /dev/ttyS2    (also known as serial port COM3)
    chmod 666 /dev/ttyS3    (also known as serial port COM4)

These commands give read/write access to everyone on the system.

An alternative method is to make the permissions 660 and add specific users to the group in which the devices reside. On a SUSE system, for example, the devices are in the uucp group. Thus, users can be added to the uucp group to gain access to the devices.

Change the access mode of any other ports as needed.

Specifying devices in the javax.comm.properties file

The file javax.comm.properties allows you to specify the prefixes of the devices that are made available to the Java Communications API and whether they are parallel or serial. Port numbers are allocated sequentially to all devices. For example, if you specify /dev/ttyS=PORT_SERIAL and the devices /dev/ttyS0 and /dev/ttyS1 exist, they will be allocated COM1 and COM2 respectively.

To use the USB-serial connectors, uncomment the line /dev/ttyUSB=PORT_SERIAL in the javax.comm.properties file. If the devices /dev/ttyUSB0 and /dev/ttyUSB1 exist and COM1 and COM2 have already been defined, the USB-serial devices are allocated the next sequential ports, COM3 and COM4.

Enabling serial ports on IBM ThinkPads

Most ThinkPads have their serial ports disabled by default in the BIOS. Currently, there is no way to enable the ports with Linux (the tpctl package does not enable the ports if they are disabled in the BIOS).

To enable the ports in the BIOS, you must use the DOS version of the ThinkPad Configuration Utility that is available from the IBM ThinkPad Download site. To use the ThinkPad Configuration Utility, you need a bootable DOS diskette. Note that the ThinkPad Configuration Utility might have been installed as part of the ThinkPad Utilities under Windows, depending on your installation options, and you can run it from a command prompt in Windows.

The ThinkPad Configuration application provided with Windows has options to enable or disable the serial and parallel ports but this does not also change the settings in the BIOS. So if you use this application with Windows, the ports are available; however, if you reboot your machine with Linux, the ports will not be enabled.

Printing limitation with the Java Communications API

When printing with the Java Communications API, you might have to press "Form feed" or "Continue" or similar on the printer.

Uninstalling Java Communications API

The process you use to uninstall the Java Communications API depends on whether you installed the installable Red Hat Package Manager (RPM) package or the compressed Tape Archive (TAR) package.

Uninstalling the installable Red Hat Package Manager (RPM) package

To uninstall the Java Communications API if you installed the installable RPM package:

  1. At a shell prompt, type:

        rpm -e ibm-java2-<arch>-javacomm-5.0-0.0     

    Alternatively, you can use a graphical tool such as kpackage or yast2.

  2. If the directory where you installed the Java Communications API does not contain any other tools that you require, remove that directory from your PATH statement.

Uninstalling the compressed Tape Archive (TAR) package

To uninstall the Java Communications API, if you installed the compressed TAR package, delete the following files from the directory where you installed them:

Java Communications API documentation

You can find API documentation and samples for Java Communications API at the Sun Web site: http://java.sun.com.

Deploying Java applications

(Linux IA 32-bit and PPC32 only) Using the Java Plug-in

The Java Plug-in is a Web browser Plug-in. If you use the Java Plug-in, you can bypass your Web browser's default JVM and instead use a Runtime Environment of your choice to run applets or beans in the browser.

You must allow applets to finish loading to prevent your browser from 'hanging'. For example, if you use the Back button and then the Forward button while an applet is loading, the HTML pages might be unable to load.

The Java Plug-in is documented by Sun at: http://java.sun.com/j2se/1.5.0/docs/guide/plugin/developer_guide/.

Supported browsers

|For Linux PPC32, Mozilla 1.6 is the supported |browser.

|For Linux IA32, see Table 3.

|Table 3. Browsers supported by the Java Plug-in on Linux IA32
|Distribution |Netscape default version |Netscape supported versions |Mozilla default version |Mozilla supported versions
|Red Hat Enterprise Linux 3.0 |- |7.x |1.4.2 |1.4.1, 1.4.2, 1.7.12, Firefox 1.0.x, 1.5
|Red Hat Enterprise Linux 4.0 |4.8 |7.x |1.7.3 |1.4.1, 1.4.2, 1.7.12, Firefox 1.0.x, 1.5
|Red Hat Enterprise Linux 5.0 |4.8 |7.x |1.7.3 |1.4.1, 1.4.2, 1.7.12, Firefox 1.0.x, 1.5
|SUSE Linux Enterprise Server 9.0 |- |7.x |1.6 |1.4.1, 1.4.2, 1.6, 1.7.12, Firefox 1.0.x, 1.5
|SUSE Linux Enterprise Server 10 |- |7.x |N/A |N/A

Installing and configuring the Java Plug-in

|Multiple versions of the Java Plug-in are supplied with |the SDK. You choose the right version for your browser. The most common |are:

| |
libjavaplugin_oji.so
|
The most common Plug-in. It is based on Mozilla's Open JVM Integration initiative and is used with most Mozilla products |and derivatives, including Firefox. |
|
libjavaplugin_ojigtk2.so
|
The same Plug-in as above but compiled with the GTK2 toolkit. |This |Plug-in can be used on Linux operating systems, such as RHEL 5, that do not |ship with the GTK1.x library, which is required by libjavaplugin_oji.so.| |

|There are instructions for installing the Plug-in on |some common browsers below.

|You must symbolically link the Plug-in, rather than |copy it, so that it can locate the JVM.

Mozilla

|Only Mozilla versions 1.4 and later are supported.

To make the Java Plug-in available to all users:

  1. Log in as root.
  2. Change to your Mozilla Plug-ins directory (this could be different on some Linux distributions) .
    cd /usr/local/mozilla/plugins/
  3. |Create a symbolic link to libjavaplugin_oji.so or libjavaplugin_ojigtk2.so |based on the available version of GTK. To use the GTK1.x library, create a |link to libjavaplugin_oji.so using: |
    ln -s /opt/ibm/java2-i386-50/jre/bin/libjavaplugin_oji.so
    To use the GTK2 library, create a link to libjavaplugin_ojigtk2.so |using: |
    ln -s /opt/ibm/java2-i386-50/jre/bin/libjavaplugin_ojigtk2.so 

You must symbolically link the Plug-in, rather than copy it, so that it can locate the JVM.

| | |

Firefox

|

To make the Java Plug-in available to all users:

|
    |
  1. Log in as root.
  2. |
  3. Change to your Firefox Plug-ins directory (this could be different |on some Linux distributions) . |
    cd /usr/local/mozilla-firefox/plugins/
  4. |
  5. |Create a symbolic link to libjavaplugin_oji.so or libjavaplugin_ojigtk2.so |based on the available version of GTK. To use the GTK1.x library, create a |link to libjavaplugin_oji.so using: |
    ln -s /opt/ibm/java2-i386-50/jre/bin/libjavaplugin_oji.so
    To use the GTK2 library, create a link to libjavaplugin_ojigtk2.so |using: |
    ln -s /opt/ibm/java2-i386-50/jre/bin/libjavaplugin_ojigtk2.so 
    |
|

You must symbolically link the Plug-in, rather than copy it, so |that it can locate the JVM.

Netscape 7.1 and above

To install and configure the Java Plug-in for Netscape, make a symbolic link from the library file /opt/ibm/java2-i386-50/jre/bin/javaplugin_oji.so to your browser's Plug-ins directory (/browser-install-path/plugins).

  1. Log in as root.
  2. Change to your Netscape Plug-ins directory (this could be different on some Linux distributions).
    cd /usr/local/netscape/plugins/
  3. Create a symbolic link to javaplugin_oji.so.
    ln -s /opt/ibm/java2-i386-50/jre/bin/javaplugin_oji.so 

You must symbolically link the Plug-in, rather than copy it, so that it can locate the JVM.

Common Document Object Model (DOM) support

Because of limitations in particular browsers, you might not be able to implement all the functions of the org.w3c.dom.html package. One of the following errors will be thrown:

Using DBCS parameters

The Java Plug-in supports double-byte characters (for example Chinese Traditional BIG-5, Korean, Japanese) as parameters for the tags <APPLET>, <OBJECT>, and <EMBED>. You must select the correct character encoding for your HTML document so that the Java Plug-in can parse the parameter. Specify character encoding for your HTML document by using the <META> tag in the <HEAD> section like this:

<meta http-equiv="Content-Type" content="text/html; charset=big5">

This example tells the browser to use the Chinese BIG-5 character encoding to parse the HTML file using. All the parameters are passed to the Java Plug-in correctly. However, some of the older versions of browsers might not understand this tag correctly. In this case, you can force the browser to ignore this tag, but you might have to change the encoding manually.

You can specify which encoding you want to use to parse the HTML file:

(Linux IA 32-bit, PPC32, and PPC64 only) Using Web Start

Java Web Start is used to deploy Java applications. Web Start allows users to launch and manage applications directly from the Web. Applications are cached to minimize installation times. Applications are automatically upgraded when new versions become available.

|Web Start supports these java-vm-args documented at http://java.sun.com/j2se/1.5.0/docs/guide/javaws/developersguide/syntax.html#resources:

IBM Web Start also supports -Xgcpolicy to set the garbage collection policy.

For information on the browsers that support Web Start, see Supported browsers.

For more information about Web Start, see: http://java.sun.com/products/javawebstart and http://java.sun.com/j2se/1.5.0/docs/guide/javaws/index.html. For more information about deploying applications, see: http://java.sun.com/j2se/1.5.0/docs/guide/deployment/index.html.

Running Web Start

Java Web Start version 5.0 is installed automatically when you install Java using the .rpm or .tgz packages.

|If you extract Java from the .tgz package, run the jre/lib/javaws/updateSettings.sh |shell script, to update the .mailcap and .mime.types files on your system.

You can invoke Web Start in three ways:

  1. Select a link on a Web page that refers to a .jnlp file.
  2. At a shell prompt, type javaws <URL>, where <URL> is the location of a .jnlp file.
  3. |If you have used Java Web Start to open the application in |the past, run /opt/ibm/java2-i386-50/jre/bin/javaws to launch the Java Application |Cache Viewer.

All Java Web Start applications are stored in the Java Application Cache. An application is only downloaded if the latest version is not in the cache.

| | |

(Linux IA 32-bit only) Secure |Static Versioning support

|

Static versioning allows Web Start applications to request a specific JVM |version to be run under. Because this capability also allows applications |to exploit old security vulnerabilities on systems which have been upgraded |to a new JVM, Secure Static Versioning (SSV) is now used by default.

|

With SSV, the user will be warned before running any unsigned Web Start |application that requests a specific JVM be used. Signed applications and |applications which request the latest version of the JVM run as normal.

|

You can disable SSV by setting the deployment.javaws.ssv.enabled property |in the deployment.properties file to false.

Shipping Java applications

A Java application, unlike a Java applet, cannot rely on a Web browser for installation and runtime services. When you ship a Java application, your software package probably consists of the following parts:

To run your application, a user needs the Runtime Environment for Linux. The SDK for Linux software contains a Runtime Environment. However, you cannot assume that your users have the SDK for Linux software installed.

Your SDK for Linux software license does not allow you to redistribute any of the SDK's files with your application. You should ensure that a licensed version of the SDK for Linux is installed on the target machine.

| | |

Class data sharing between JVMs

|

The IBM Virtual Machine (VM) allows you to share bootstrap and application |classes between VMs by storing them in a cache in shared memory. Class sharing |reduces the overall virtual memory consumption when more than one VM shares |a cache. Class sharing also reduces the startup time for a VM after the cache |has been created. The shared class cache is independent of any active VM and |persists beyond the lifetime of the VM that created the cache.

| |

Overview of class sharing

|

The IBM SDK allows you to share as many classes as possible, while appearing |transparent to the user.

| |

Cache contents

|

The shared class cache contains read-only static class data and metadata |that describes the classes. Any VM may read or update the cache. The VMs that |are sharing must be at the same release. You must take care if runtime bytecode |modification is being used. (See Runtime bytecode modification.)

| |

Dynamic updating of the cache

|

Because the shared class cache persists beyond the lifetime of any VM, |the cache is updated dynamically to reflect any modifications that might have |been made to JARs or classes on the file system. The dynamic updating makes |the cache transparent to the application using it.

| |

Enabling class sharing

|

Enable class sharing by using the -Xshareclasses option |when starting a VM, to make the VM connect to an existing cache or to create |one if it does not exist. All bootstrap and application classes loaded by |the VM are shared by default. Custom class loaders share automatically if |they extend the application class loader; otherwise, they must use the Java |Helper API provided with the VM to access the cache. (See Adapting custom classloaders to share classes.)

| |

Cache security

|

Access to the shared class cache is limited by operating system permissions |and Java security permissions. The shared class cache |is created with user access by default unless the groupAccess command-line suboption is used. Only a class loader that has registered |to share classes can add classes to the shared class cache. If a Java SecurityManager |is installed, class loaders, excluding the default bootstrap, application, |and extension class loaders, must be granted permission to share classes by |adding SharedClassPermission lines to the java.policy file. (See Using SharedClassPermission.) |The RuntimePermission "createClassLoader" restricts the creation of new class |loaders and therefore also restricts access to the cache.

| |

Cache lifespan

|

Multiple caches can exist on a system and are specified by name as a suboption |to the -Xshareclasses command. A VM can connect to only |one cache at any one time. You specify cache size on startup using -Xscmx<n>[k|m|g], but this size is then fixed for the lifetime of |the cache. Caches exist until they are explicitly destroyed using a suboption |to the -Xshareclasses command or until the system is |rebooted.

| |

Cache utilities

|

All cache utilities are suboptions to the -Xshareclasses command. Use -Xshareclasses:help to see a list |of available suboptions.

| |

Using command-line options for class sharing

|

Use the -Xshareclasses and -Xscmx command-line options to enable and configure class sharing.

| | |

Creating, populating, monitoring, and deleting a cache

|

To enable class sharing, add -Xshareclasses[:name=<name>] to your application command line. The VM will either connect to an existing |cache of the given name, or create a new cache of that name. If a new cache |has been created, it will be populated with all bootstrap and application |classes being loaded until the cache becomes full. If two or more VMs are |started concurrently, they will all populate the cache concurrently.

|

To check that the cache has been created, run java -Xshareclasses:listAllCaches. To see how many classes and how much class data is being shared, run java -Xshareclasses:[name=<name>],printStats. (These utilities can |be run after the application VM has terminated or in another command window.)

|

For more feedback on cache usage while the VM is running, use the verbose suboption. For example, java -Xshareclasses:[name=<name>],verbose.

|

To see classes being loaded from the cache or stored in the cache, add |-Xshareclasses:[name=<name>],verboseIO| to your application |command line.

|

To delete the cache created, run java -Xshareclasses:[name=<name>],destroy. You should have to delete caches only if they contain many stale |classes or if the cache is full and you want to create a bigger cache.

|

You are recommend to tune the cache size for your specific application, |because the default is unlikely to be the optimum size. The best way to determine |the optimum cache size is to specify a large cache (using -Xscmx), run the application, and then use printStats to determine how |much class data has been stored. Add a small amount to the value shown in |printStats for contingency. Note that because classes can be loaded at any |time during the lifetime of the VM, it is best to do this analysis after the |application has terminated. However, a full cache does not have a negative |impact on the performance or capability of any VMs connected to it, so it |is quite legitimate to decide on a cache size that is smaller than required.

|

If a cache becomes full, a message is output to the command line of any |VMs using verbose suboption. All VMs sharing the full cache will then load |any further classes into their own process memory. Classes in a full cache |can still be shared, but a full cache is read-only and cannot be updated with |new classes.

| |

Performance and memory consumption

|

Class sharing is particularly useful on systems that use more than one |VM running similar code; the system benefits from reduced virtual memory consumption. | It is also useful on systems that frequently start up and shut down VMs, |which benefit from the improvement in startup time.

|

The overhead to create and populate a new cache is minimal. The VM startup |cost in time for a single VM is typically between 0 and 5% slower compared |with a system not using class sharing, depending on how many classes are loaded. |VM startup time improvement with a populated cache is typically between 10% |and 40% faster compared with a system not using class sharing, depending on |the operating system and the number of classes loaded. Multiple VMs running |concurrently will show greater overall startup time benefits.

|

|Duplicate classes are consolidated within the shared class |cache. For example, class A loaded from myClasses.jar and class A loaded from |myOtherClasses.jar (with identical content) is stored only once in the cache. |The printAllStats utility shows multiple entries for duplicated classes, with |each entry pointing to the same class.|

|

When you run your application with class sharing, you can use the operating |system tools to see the reduction in virtual memory consumption.

| |

Limitations and considerations of using class sharing

| |

Cache size limits

|

The cache for sharing classes is allocated using System |V IPC Shared memory mechanism.

|

The maximum theoretical cache size is 2 GB. The size of cache |you can specify is limited by the amount of physical memory and paging space available to the system.

|

Because the virtual address space of a process is shared |between the shared classes cache and the Java heap, increasing the maximum |size of the Java heap will reduce the size of the shared classes cache you |can create.

|

Cache size is limited by SHMMAX settings, |which limits the amount of shared memory that can be allocated. You can find |these settings by looking at /proc/sys/kernel/shmmax file. SHMMAX is usually set to 30MB.

| |

Runtime bytecode modification

|

|Any VM using a JVMTI (JVM Tool Interface) agent that can |modify bytecode data should use the modified=<modified_context> suboption |if it wants to share the modified classes with another VM. (See Using command-line options for class sharing.) |The modified context is a user-specified descriptor that describes the type |of modification being performed. The modified context partitions the cache |so that all VMs running under the same context share a partition. This partitioning |allows VMs that are not using modified bytecode to safely share a cache with |those that are using modified bytecode. All VMs using a given modified context |must modify bytecode in a predictable, repeatable manner for each class, so |that the modified classes stored in the cache have the expected modifications |when they are loaded by another VM. Any modification must be predictable because |classes loaded from the shared class cache cannot be modified again by the |agent.|

|

|If a JVMTI agent is used without a modification context, |classes are still safely shared by the VM, but with a small impact on performance. |Using a modification context with a JVMTI agent avoids the need for extra |checks and therefore has no impact on performance. A custom ClassLoader that |extends java.net.URLClassLoader and modifies bytecode at load time without |using JVMTI automatically stores that modified bytecode in the cache, but |the cache does not treat the bytecode as modified. Any other VM sharing that |cache loads the modified classes. The modified=<modification_context> suboption can be used in the same way as with JVMTI agents to partition |modified bytecode in the cache. If a custom ClassLoader needs to make unpredictable |load-time modifications to classes, that ClassLoader must not attempt to use |class sharing.|

|

See the Diagnostics Guide for more detail |on this topic.

| |

Operating system limitations

|

For operating systems that can run both 32-bit and 64-bit |applications, class sharing is not permitted between 32-bit and 64-bit VMs. |The listAllCaches suboption lists 32-bit or 64-bit caches, |depending on the address mode of the VM being used.

|

The shared class cache requires disk space to store identification information |about the caches that exist on the system. This information is |stored in /tmp/javasharedresources. If the identification information |directory is deleted, the VM cannot identify the shared classes on the system |and must recreate the cache. Use the ipcs command |to view the memory segments used by a VM or application.

|

Users running a JVM must be in the same group to use a |shared class cache. The permissions for accessing a shared classes cache |are enforced by the operating system. If a cache name is not specified, the |user name is appended to the default name so that multiple users on the same |system create their own caches by default.

| |

Using SharedClassPermission

|

If a SecurityManager is being used with class sharing and the running application |uses its own classloaders, these classloaders must be granted shared class |permissions before they can share classes. You add shared class permissions |to the java.policy file using the ClassLoader class name (wildcards are permitted) |and either "read", "write", or "read,write" to determine the access granted. |For example:

|
permission com.ibm.oti.shared.SharedClassPermission
|        "com.abc.customclassloaders.*", "read,write";

If a ClassLoader |does not have the correct permissions, it is prevented from sharing classes. | You cannot change or reduce the permissions of the default bootstrap, application, |or extension classloaders.

| |

Adapting custom classloaders to share classes

|

Most Java applications use the VM's own classloaders or have custom classloaders |that extend java/net/URLClassLoader. Applications using these classloaders |can automatically share bootstrap and application classes. Custom classloaders |that do not extend java/net/URLClassLoader will require modifications to make |use of class sharing. All custom class loaders must be granted shared class |permissions if a SecurityManager is being used, see Using SharedClassPermission. |IBM provides several Java interfaces for various types of custom classloaders, |which allow the classloaders to find and store classes in the shared class |cache. These classes are in the com.ibm.oti.shared package. The Javadoc for |this package is provided with the SDK in the file docs/apidoc.zip. See the Diagnostics Guide for more information on |how to use these interfaces.

Service and support for independent software vendors

If you are entitled to services for the Program code pursuant to the IBM Solutions Developer Program, contact the IBM Solutions Developer Program through your normal method of access or on the Web at: http://www-1.ibm.com/partnerworld/.

If you have purchased a service contract (that is, IBM's Personal Systems Support Line or equivalent service by country), the terms and conditions of that service contract determine what services, if any, you are entitled to receive with respect to the Program.

Accessibility

The User Guides that are supplied with this SDK and the Runtime Environment have been tested by using screen readers. You can use a screen reader such as the Home Page Reader or the JAWS screen reader with these User Guides.

To change the font sizes in the User Guides, use the function that is supplied with your browser, usually found under the View menu option.

For users who require keyboard navigation, a description of useful keystrokes for Swing applications is in "Swing Key Bindings" at http://www-128.ibm.com/developerworks/java/jdk/additional/

iKeyman accessibility

|In addition to the GUI, the iKeyman tool provides the command-line |tool IKEYCMD, which has the same functions that the |iKeyman GUI has. IKEYCMD allows you to manage keys, |certificates, and certificate requests. You can call IKEYCMD from native shell scripts and from programs that are to be used when |applications need to add custom interfaces to certificate and key management |tasks. IKEYCMD can create key database files for all |the types that iKeyman currently supports. IKEYCMD can |also create certificate requests, import CA signed certificates, and manage |self-signed certificates.

To run an IKEYCMD command, enter:

java [-Dikeycmd.properties=<properties file>] com.ibm.gsk.ikeyman.ikeycmd
<object> <action> [options]

where:

<object>
is one of the following:
-keydb
Actions that are taken on the key database (either a CMS key database file, a WebDB keyring file, or SSLight class)
-cert
Actions that are to be taken on a certificate within a key database
-certreq
Actions that are to be taken on a certificate request within a key database
-version
Displays version information for IKEYCMD
-help
Displays help for the IKEYCMD invocations.
<action>
|The specific action that is to be taken on the object. To |see the available actions for an object, invoke IKEYCMD passing |only the object as an argument. Context-sensitive help shows the available |actions for that object.
-Dikeycmd.properties
Specifies the name of an optional properties file to use for this Java invocation. A default properties file, ikeycmd.properties, is provided as a sample file that can be changed and used by any Java application.
Note:
The object and action keywords must be in the specified sequence. However, options are not positional and can be in any sequence, provided that they are specified as an option and operand pair.

For more information, see the iKeyman User Guide at: http://www.ibm.com/developerworks/java/jdk/security/index.html.

Keyboard traversal of JComboBox components in Swing

If you traverse the drop-down list of a JComboBox component with the cursor keys, the button or editable field of the combo box does not change value until an item is selected. This is the desired behavior for this release and improves accessibility and usability by ensuring that the keyboard traversal behavior is consistent with mouse traversal behavior.

(Linux IA 32-bit, PPC32, and PPC64 only) Web Start accessibility

Web Start v5.0 contains several accessibility and usability improvements over the previous release, including better support for screen readers and improved keyboard navigation.

You can use the command line only to launch a Java application that is enabled for Web Start. To change preference options, you must edit a configuration file, .java/.deployment/.deployment.properties in the user's home directory. Take a backup before you edit this file. Not all the preferences that can be set in the Java Application Cache Viewer are available in the configuration file.

Known limitations

The following sections explain known limitations of the SDK and Runtime Environment for Linux.

Limitations that apply to all Linux platforms except where indicated

Linux IA 32-bit limitations

Linux AMD64 limitations

Linux PPC 32-bit and 64-bit limitations

Linux PPC 64-bit limitations

Linux zSeries 64-bit limitations

The following limitations apply to Chinese and Taiwanese users on Linux zSeries 64-bit:

Linux zSeries 31-bit and 64-bit limitations

Any comments on this User Guide?

If you have any comments about the usefulness, or otherwise, of this User Guide, we would be pleased to hear from you through one of these channels. Please note that these channels are not set up to answer technical queries, but are for comments about the documentation only. Send your comments:

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Notices

This information was developed for products and services offered in the U.S.A. IBM may not offer the products, services, or features discussed in this document in other countries. Consult your local IBM representative for information on the products and services currently available in your area. Any reference to an IBM product, program, or service is not intended to state or imply that only that IBM product, program, or service may be used. Any functionally equivalent product, program, or service that does not infringe any IBM intellectual property right may be used instead. However, it is the user's responsibility to evaluate and verify the operation of any non-IBM product, program, or service.

IBM may have patents or pending patent applications covering subject matter in this document. The furnishing of this document does not give you any license to these patents. You can send license inquiries, in writing, to:

For license inquiries regarding double-byte (DBCS) information, contact the IBM Intellectual Property Department in your country or send inquiries, in writing, to:

The following paragraph does not apply to the United Kingdom or any other country where such provisions are inconsistent with local law:

INTERNATIONAL BUSINESS MACHINES CORPORATION PROVIDES THIS PUBLICATION "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Some states do not allow disclaimer of express or implied warranties in certain transactions, therefore, this statement may not apply to you.

This information could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein; these changes will be incorporated in new editions of the information. IBM may make improvements and/or changes in the product(s) and/or the program(s) described in this information at any time without notice.

Any references in this information to non-IBM Web sites are provided for convenience only and do not in any manner serve as an endorsement of those Web sites. The materials at those Web sites are not part of the materials for this IBM product and use of those Web sites is at your own risk.

IBM may use or distribute any of the information you supply in any way it believes appropriate without incurring any obligation to you.

Licensees of this program who wish to have information about it for the purpose of enabling (i) the exchange of information between independently created programs and other programs (including this one) and (ii) the mutual use of the information which has been exchanged, should contact:

Such information may be available, subject to appropriate terms and conditions, including in some cases, payment of a fee.

The licensed program described in this document and all licensed material available for it are provided by IBM under terms of the IBM Customer Agreement, IBM International Program License Agreement or any equivalent agreement between us.

Any performance data contained herein was determined in a controlled environment. Therefore, the results obtained in other operating environments may vary significantly. Some measurements may have been made on development-level systems and there is no guarantee that these measurements will be the same on generally available systems. Furthermore, some measurement may have been estimated through extrapolation. Actual results may vary. Users of this document should verify the applicable data for their specific environment.

Information concerning non-IBM products was obtained from the suppliers of those products, their published announcements or other publicly available sources. IBM has not tested those products and cannot confirm the accuracy of performance, compatibility or any other claims related to non-IBM products. Questions on the capabilities of non-IBM products should be addressed to the suppliers of those products.

Trademarks

IBM, iSeries, pSeries, and zSeries are trademarks or registered trademarks of International Business Machines Corporation in the United States, or other countries, or both.

Intel is a trademark of Intel Corporation in the United States, other countries, or both.

Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc. in the United States, other countries, or both.

Linux is a trademark of Linus Torvalds in the United States, other countries, or both.

Other company, product, or service names may be trademarks or service marks of others.

This product is also based in part on the work of the FreeType Project. For more information about Freetype, see http://www.freetype.org.

This product includes software developed by the Apache Software Foundation http://www.apache.org/.