IBM User Guide for Java V7 on Windows > Reference > Environment variables

JVM environment settings

This section describes common environment settings. The categories of settings are general options, deprecated JIT options, Javadump and Heapdump options, and diagnostic options.

General options

The following list summarizes common options. It is not a definitive guide to all the options. Also, the behavior of individual platforms might vary. See individual sections for a more complete description of behavior and availability of these variables.

CLASSPATH=<directories and archive or compressed files>

Set this variable to define the search path for application classes and resources. The variable can contain a list of directories for the JVM to find user class files and paths to individual Java™ archive or compressed files that contain class files; for example, /mycode:/utils.jar (UNIX or i5/OS™), D:\mycode;D:\utils.jar (Windows).

Any class path that is set in this way is replaced by the -cp or -classpath Java argument if used.

IBM_JAVA_COMMAND_LINE

This variable is set by the JVM after it starts. Using this variable, you can find the command-line parameters set when the JVM started.

This setting is not available if the JVM is invoked using JNI.

IBM_JAVA_OPTIONS=<option>

Set this variable to store default Java options including -X, -D or -verbose:gc style options; for example, -Xms256m -Djava.compiler.

Any options set are overridden by equivalent options that are specified when Java is started.

This variable does not support -fullversion or -version.

If you specify the name of a trace output file either directly, or indirectly, using a properties file, the output file might be accidentally overwritten if you run utilities such as the trace formatter, dump extractor, or dump viewer. For information about avoiding this problem, see Controlling the trace, Note these restrictions.

JAVA_ASSISTIVE={ OFF | ON }

Set the JAVA_ASSISTIVE environment variable to OFF to prevent the JVM from loading Java Accessibility support.

JAVA_FONTS=<list of directories>

Set this environment variable to specify the font directory. Setting this variable is equivalent to setting the properties java.awt.fonts and sun.java2d.fontpath.

LIBPATH=<list of directories>

Set this variable to a colon-separated list of directories to define from where system and user libraries are loaded. You can change which versions of libraries are loaded, by modifying this list.

This variable is for AIX, i5/OS, and z/OS only.

Deprecated JIT options

The following list describes deprecated JIT options:

IBM_MIXED_MODE_THRESHOLD

Use -Xjit:count=<value> instead of this variable.

JAVA_COMPILER

Use -Djava.compiler=<value> instead of this variable.

Javadump and Heapdump options

The following list describes the Javadump and Heapdump options. The recommended way of controlling the production of diagnostic data is the -Xdump command-line option, described in Using dump agents.

DISABLE_JAVADUMP={ TRUE | FALSE }

This variable disables Javadump creation when set to TRUE.

Use the command-line option -Xdisablejavadump instead. Avoid using this environment variable because it makes it more difficult to diagnose failures.

IBM_HEAPDUMP or IBM_HEAP_DUMP={ TRUE | FALSE }

These variables control the generation of a Heapdump.

When the variables are set to 0 or FALSE, Heapdump is not available. When the variables are set to anything else, Heapdump is enabled for crashes or user signals. When the variables are not set, Heapdump is not enabled for crashes or user signals.

IBM_HEAPDUMP_OUTOFMEMORY={ TRUE | FALSE }

This variable controls the generation of a Heapdump when an out-of-memory exception is thrown.

When the variable is set to TRUE or 1 a Heapdump is generated each time an out-of-memory exception is thrown, even if it is handled. When the variable is set to FALSE or 0, a Heapdump is not generated for an out-of-memory exception. When the variable is not set, a Heapdump is generated when an out-of-memory exception is not caught and handled by the application.

IBM_HEAPDUMPDIR=<directory>

This variable specifies an alternative location for Heapdump files.

IBM_JAVACOREDIR=<directory>

This variable specifies an alternative location for Javadump files; for example, on Linux IBM_JAVACOREDIR=/dumps

IBM_JAVADUMP_OUTOFMEMORY={ TRUE | FALSE }

This variable controls the generation of a Javadump when an out-of-memory exception is thrown.

When the variable is set to TRUE or 1, a Javadump is generated each time an out-of-memory exception is thrown, even if it is handled. When the variable is set to FALSE or 0, a Javadump is not generated for an out-of-memory exception. When the variable is not set, a Javadump is generated when an out-of-memory exception is not caught and handled by the application.

IBM_NOSIGHANDLER={ TRUE }

This variable disables the signal handler when set to any value. If no value is supplied, the variable has no effect and the signal handler continues to work.

The variable is equivalent to the command-line option -Xrs:all

JAVA_DUMP_OPTS=<value>

This variable controls how diagnostic data are dumped.

For a fuller description of JAVA_DUMP_OPTS and variations for different platforms, see Dump agent environment variables.

TMPDIR=<directory>

This variable specifies an alternative temporary directory. This directory is used only when Javadumps and Heapdumps cannot be written to their target directories, or the current working directory.

This variable defaults to /tmp on Linux, z/OS, AIX, and i5/OS. This variable defaults to C:\Temp on Windows.

Diagnostics options

The following list describes the diagnostics options:

IBM_COREDIR=<directory>

Set this variable to specify an alternative location for system dumps and snap trace.

On z/OS, _CEE_DMPTARG is used instead for snap trace, and transaction dumps are written to TSO according to JAVA_DUMP_TDUMP_PATTERN.

On Linux, the dump is written to the OS specified directory, before being moved to the specified location.

IBM_JVM_DEBUG_PROG=<debugger>

Set this variable to start the JVM under the specified debugger.

This variable is for Linux only.

IBM_MALLOCTRACE=TRUE

Setting this variable to a non-null value lets you trace memory allocation in the JVM. You can use this variable with the -Dcom.ibm.dbgmalloc=true system property to trace native allocations from the Java classes.

This variable is equivalent to the command-line option -Xcheck:memory.

IBM_XE_COE_NAME=<value>

Set this variable to generate a system dump when the specified exception occurs. The value supplied is the package description of the exception; for example, java/lang/InternalError.

A Signal 11 is followed by a JVMXE message and then the JVM terminates.

JAVA_PLUGIN_TRACE=TRUE

When this variable is set to TRUE or 1, a Java plug-in trace is produced for the session when an application runs. Traces are produced from both the Java and Native layer.

By default, this variable is set to FALSE, so that a Java plug-in trace is not produced.

Parent: Environment variables

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