IBM User Guide for Java V7 on Windows > Reference



Known issues and limitations

Problems that you might encounter in specific system environments, or configurations.

The problems described in this topic might not be limitations with the SDK or JRE. Instructions are provided to work around problems, where possible.


Chinese characters stored as ? in an Oracle database

When you configure an Oracle database to use the ZHS16GBK character set, some Chinese characters or symbols that are encoded with the GBK character set are incorrectly stored as a question mark (?). This problem is caused by an incompatibility of the GBK undefined code range Unicode mapping between the Oracle ZHS16GBK character set and the IBM GBK converter. To fix this problem, use a new code page, MS936A, by including the following system property when you start the JVM:

For IBM WebSphere Application Server users, this problem might occur when web applications that use JDBC configure Oracle as the WebSphere Application Server data source. To fix this problem, use a new code page, MS936A, as follows:

  1. Use the following system property when you start the JVM:

      -Dfile.encoding=MS936A

  2. Add the following lines to the WAS_HOME/properties/converter.properties file, where WAS_HOME is your WebSphere Application Server installation directory. 
    GBK=MS936A
GB2312=MS936A


IPv6 support on Windows XP and Windows 2003

Java 7 introduces a new NIO.2 API for asynchronous input/output (IO). However, sockets created with the NIO.2 APIs support only IPv4 network interfaces on the Windows XP and Windows 2003 platforms. The IBM implementation of NIO.2 is consistent with this behavior.

Although sockets created with the earlier IBM NIO APIs or java.net can support either IPv4 or IPv6 network interfaces on Windows 2003 and Windows XP, this capability is deprecated in this release and will be removed from future releases.

These known issues and limitations also apply to earlier releases of the SDK and JRE:


Web Start and IBM SDK for Java, v1.3 applications

The IBM 64-bit SDK for Windows, v7 Web Start does not support launching IBM SDK for Java 1.3 applications.


Unicode Shift_JIS code page alias

Note: This limitation applies to Japanese users only. The Unicode code page alias "\u30b7\u30d5\u30c8\u7b26\u53f7\u5316\u8868\u73fe" for Shift_JIS has been removed. If you use this code page in your applications, replace it with Shift_JIS.


-Xshareclasses:<options>

Shared class caches and control files are not compatible between IBM SDK for Java v7 and IBM SDK for Java v6 SR3 or previous releases.


Font problems in supported locales

The IBM 64-bit SDK for Windows, v7 supports the following locales:

However, the fonts from these locales might not work on AWT components.


Use of sockets with IPv6

The IBM 64-bit SDK for Windows, v7 supports IPv6. However, because the current IPv6 support in Windows is not dual-stack, the IBM SDK emulates dual-stack behavior on an IPv6 enabled system. The emulation means that your IBM Java application might use up to twice as many sockets.

To disable the emulation, disable IPv6 support in the SDK by setting the system property java.net.preferIPv4Stack to true.


Input Method Editor (IME)

When working with an Input Method Editor (IME), before using the workspace for any other operation ensure that you complete the character composition and select the candidate.

If a user types text in an AWT TextArea while using an Input Method Editor (IME), then resizes the application window before committing the text, the text is committed automatically.


DBCS characters

If you are typing DBCS characters in a JTextArea, JTextField, or JFileChooser, switching from some Chinese IMEs (in particular, Chinese Internal Code and Zhengma) to Intelligent ABC IME might cause a core dump to be produced.


Japanese MS-IME and Windows XP Professional Themes

If you use the Japanese MS-IME on Windows XP Professional x64 Edition, the 64-bit IBM SDK might cause errors with Windows XP Professional Themes.

To avoid these errors, set the environmental variable IBMJAVA_USE_WINDOWS_CLASSIC_THEME to force the IBM Java GUI windows to display by using the Windows classic theme. Alternatively, change your system theme to Windows classic.

For more information about this limitation, available in Japanese only, see Microsoft Knowledge Base Article 905843.


BIOS settings on AMD64 SMP systems

The Node memory interleaving BIOS setting must be set to DISABLED. Otherwise, unpredictable results might occur, including Java crashes and hangs. This instruction is in accordance with recommendations from AMD.


Using -Xshareclasses:destroy during JVM startup

When running the command java -Xshareclasses:destroy on a shared cache that is being used by a second JVM during startup, you might have the following issues:

Changes to locale translation files

From Java 7 service refresh 1, changes are made to the locale translation files to make them consistent with Oracle JDK 7. The same changes were applied to the IBM SDK for Java 6 for consistency with Oracle JDK 6. To understand the differences in detail, see this Java 6 support document:http://www.ibm.com/support/docview.wss?uid=swg21568667.

Large page request fails

There is no error message issued when the JVM is unable to honor the -Xlp request.

There are a number of reasons why the JVM cannot honor a large page request. For example, there might be insufficient large pages available on the system at the time of the request. To check whether the -Xlp request was honored, you can review the output from -verbose:gc. Look for the attributes requestedPageSize and pageSize in the -verbose:gc log file. The attribute requestedPageSize contains the value specified by -Xlp. The attribute pageSize is the actual page size used by the JVM.

Inconsistent timers on multicore or multiprocessor systems

On some multicore or multiprocessor systems, System.nanoTime() might not increase monotonically. Alternatively, System.nanoTime() might exhibit unexpectedly large time jumps. This behavior might be caused by a limitation in the Windows function QueryPerformanceCounter(). For more information, see Microsoft Knowledge Base article: http://support.microsoft.com/kb/895980.

ThreadMXBean thread CPU time might not be monotonic on SMP systems

On SMP systems, the times returned by ThreadMXBean.getThreadUserTime(), ThreadMXBean.getThreadCpuTime(), ThreadMXBean.getCurrentThreadUserTime(), and ThreadMXBean.getCurrentThreadCpuTime() might not increase monotonically if the relevant thread migrates to a different processor.

AESNI support on x86 platforms

Software exploitation of AESNI instructions on x86 architectures is currently not supported with the balanced or metronome GC policies.


Parent: Reference








Error 404 - Not Found

Error 404 - Not Found

The document you are looking for may have been removed or re-named. Please contact the web site owner for further assistance.