Using BEA WebLogic JRockit 7.0 JVM Command Line Options

This section describes how to use WebLogic JRockit 7.0 JVM's command line options. WebLogic JRockit supports all the standard Java command line options plus numerous extended options.

This section includes information on the following subjects:

• Using Standard Command Line Options
• Using the -X Options

Note: If WebLogic JRockit 7.0 JVM behaves in some unexpected way, please consult the WebLogic JRockit 7.0 SDK FAQ. If that doesn't solve your problem, please send an e-mail to [e-mail]

 

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Using Standard Command Line Options

The following are the standard command line options you can use with WebLogic JRockit 7.0 JVM:

• -classpath <directories and zips/jars separated by : or ;>

Tells WebLogic JRockit 7.0 JVM where to look for classes and resources.

Use a semicolon to separate entries on Windows systems and a colon on Linux.

• -cp <directories and zips/jars separated by : or ;>

This is short for -classpath.

• -D<name>[=<value>]

Tells WebLogic JRockit 7.0 JVM to set a Java system property. These can be read by a Java program, using the methods in java.lang.System.

• -version

Tells WebLogic JRockit 7.0 JVM to display its product version number and then exit.

• -showversion

Tells WebLogic JRockit 7.0 JVM to display its product version number and then continue.

• -verbose[:<components separated by ,>]

Tells WebLogic JRockit 7.0 JVM to display verbose output. This option is used mainly for debugging purposes and causes a lot of output to the console. Supported components are memory, load and codegen. If no component is given, WebLogic JRockit 7.0 JVM will display verbose information on everything.

• -help

Tells WebLogic JRockit 7.0 JVM to display a short help message.

• -X

Tells WebLogic JRockit 7.0 JVM to display a short help message on the extended options.

 

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Using the -X Options

The -X command line options are used to change the behavior of WebLogic JRockit 7.0 JVM to better suit the needs of different Java applications.

• -Xbootclasspath:<directories and zip/jar files separated by ; or :>

Tells WebLogic JRockit 7.0 JVM where to look for the Java 2 class libraries. Use this option only if you want to run WebLogic JRockit with class libraries other than those provided with the default installation. Use semicolons to separate entries on Windows systems and colons to separate entries on Linux.

• -Xms<size>[m|M|k|K]

Specifies the initial heap size in megabytes [m|M] or kilobytes [k|K].

• -Xmx<size>[m|M|k|K]

Specifies the maximum heap size in megabytes [m|M] or kilobytes [k|K].

Default is 75% of physical memory.

• -Xss<size>[k|K]

Sets the thread stack size in kilobytes.

• -Xgc:[gencopy|gencon|singlecon|parallel]

Specifies which type of garbage collector to use:

gencopy	Generational Copying
gencon	Generational Concurrent
singlecon	Single Spaced Concurrent
parallel	Parallel


 

Default is gencopy if -Xmx is set to less than 128M and gencon if it is set to more.

• -Xns<size>[m|M|L|K]

Sets the initial nursery size for generational collectors.

• -Xallocationtype:<global|local>

Sets the type of allocation to perform.

• Global—all threads allocate from the same heap. This is the default for the gencopy garbage collection method.
• Local—each thread allocates from its own heap-area. Local allocation is faster if you know that the number of threads is low. This is the default for the singlecon, gencon and parallel garbage collection methods.
• -Xcleartype:<gc|local|alloc>

Clears memory during garbage collection, either when a new thread local area is allocated or when an object is allocated, alloc is not available on IA64.

• -Xnoclassgc

Switches off garbage collection of classes.

• -Xgcreport

Writes an extensive memory management report at the end of a run.

• -Xgcpause

Prints pause times caused by the garbage collector.

• -Xnoopt

Tells WebLogic JRockit not to optimize code.

• -Xnativethreads

Tells WebLogic JRockit to use operating system threads instead of the WebLogic JRockit 7.0 JVM high performance threading system (thin threads). The default, if neither -Xnativethreads nor -Xthinthreads is specified, is to use -Xnativethreads.

• -Xthinthreads

Tells WebLogic JRockit to use the WebLogic JRockit 7.0 JVM high performance threading system instead of the operating system threads. This option is recommended when running applications with a large number of threads (more than several hundred).

Note: -Xthinthreads is not available on IA64.

• -Xverify

Do complete bytecode verification.

• -Xquiet

Tells WebLogic JRockit not to dump any informational output to stdout or stderr.

DISCLAIMER: The -X options are non-standard and subject to change without notice.