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BEA JRockit JDK Command Line Options by Name

BEA JRockit uses the command line options listed on this page for configuration and tuning.

 

Option Name Description Used In
-classpath
-cp		 Sets the path to classes and resources. Configuration
-client Starts JRockit in client mode. This option is useful when you are using a small heap and are anticipating relatively short runtimes.
By setting the JVM mode (or accepting the default) also sets the garbage collection algorithm that will be used during runtime. -client will start a single-spaced, concurrent mark, concurrent sweep garbage collector (see Using the WebLogic JRockit Memory Management System for more information).		 Configuration
-D Sets a Java system property. These can be read by a Java program, using the methods in java.lang.System. Configuration
-help Displays a short help message. Configuration
-jrockit Starts JRockit in server mode. This option does the same as starting the JVM with the option -server.  
-server Starts JRockit in server mode. This value is default.
By setting the JVM mode (or accepting the default) also sets the garbage collection algorithm that will be used during runtime. -server starts a dynamic garbage collector that is optimized for throughput (see Using the WebLogic JRockit Memory Management System for more information).		 Configuration
-showversion Displays the product version of JRockit and then continues with startup. Configuration
-verbose See -Xverbose. Configuration
-version Displays the product version of JRockit and then exits. Configuration
-X Displays a short help message on the extended options and then exits. Configuration
-Xbootclasspath Sets the search path for bootstrap classes and resources for JRockit to use instead of those supplied with the J2SE JDK. Specify the names of the directories, .zip, and .jar files, separated by ";" (Windows) or ":" (Linux). Configuration
-Xbootclasspath/a Sets the search path for bootstrap classes and resources for JRockit to use instead of those supplied with the J2SE JDK and appends the information to the default bootstrap class path.

Example:
-Xbootclasspath/a:/path/to/classes 		Configuration
-Xbootclasspath/p Sets the search path for bootstrap classes and resources for JRockit to use instead of those supplied with the J2SE JDK and prepends the information to the default bootstrap class path.

Example:
-Xbootclasspath/p:/path/to/classes 		Configuration
-Xdebug

Enables debugging support in JRockit.

Note!
This option should not be used in a production environment.

  
-Xgc:[garbage collector] Deploys the specified fixed garbage collector.

Parameters:
  • singlecon: Single-spaced concurrent
  • gencon: Generational concurrent
  • parallel: Single-spaced parallel
 Memory Management
-Xgcpause
-Xverbose:gcpause 		Both these options print the pause times that have been caused by the garbage collector. (See -Xverbose.) Memory Management
-Xgcprio:[priority] Sets the dynamic garbage collector according to the specified priority:
  • throughput: The garbage collector works as effectively as possible, giving as much CPU resources to the Java threads as possible.
  • pausetime: The garbage collector limits the length of each garbage collection pause where all threads are stopped for garbaage collection. Use -Xpausetarget to set a target length for the garbage collection pauses.
 Memory Management
-Xgcreport Prints a comprehensive garbage collection report at the end of the application run. Memory Management
-Xjvmpi Enables and disables groups of JVMPI events when running JVMPI. The events are:
  • entryexit (default is ON)
  • allocs (default ON)
  • monitors (default (ON)

Note:
JVMPI has been replaced by JVMTI for the Java 5 JDK, but it is still supported. 		Configuration
-Xmanagement:[param1=,param2=,...] Enables the management server in the VM, which needs to be started before the Management Console can connect to JRockit JVM.

By using the class= and classpath= parameters with -Xmanagement (-Xmanagement:class=, classpath=) you can specify a management class and its classpath. This option loads the class and causes its empty constructor to be called early in JVM startup. From the constructor, a new thread is then started, from which your management client is run. 		BEA JRockit Management Console
-Xms Sets the initial size of the heap. This value can be specified in kilobytes (K,k), megabytes (M,m), or gigabytes (G,g).

Default:
The default value depends upon the JVM mode:
  • -server mode: The default value is the lesser of 25% of the free physical memory or 64 MB.
  • -client mode: The default value is the lesser of 25% of the free physical memory or 16 MB.
 Tuning
-Xmx Sets the maximum size of the heap. This value can be specified in kilobytes (K,k), megabytes (M,m), or gigabytes (G,g).
Use the following guidelines to determine this value:

Default:
The default value is the lesser of 75% of the total physical memory or 1 GB. 		Tuning
-Xnoclassgc Disables garbage collection of classes. Memory Management
-Xnohup
-Xrs		 Stops JRockit from watching or process CTRL_LOGOFF_EVENT or SIGHUP events.  
-Xnoopt Stops JRockit from optimizing code. Configuration
-Xns Sets the size of the nursery in generational garbage collectors.
JRockit JVM has no specific rule regarding the maximum size of a nursery; however, it will never be larger than 95% of the current heap size.

Default:
The default initial value depends upon the JVM mode. The following is true if a generational garbage collector is used:
  • -server mode: the default nursery size is 10 MB per CPU; for example, the default for a 4 CPU system would be 40 MB.
  • -client mode: the default nursery size is 2 MB.
 Tuning
-Xpausetarget Sets a target value for the garbage collection pause lengths when running with pausetime priority (-Xgcprio:pausetime). This value can be specified in seconds (s) or milliseconds (ms).

The pausetarget is used as a guideline for the garbage collector and is used on "best effort" basis. Longer pauses may occur if it is required to avoid a premature OutOfMemory error.

Default:
The default value is 500 ms.

  
-Xss

Sets the thread stack size. This value can be specified in kilobytes (K,k), megabytes (M,m), or gigabytes (G,g).

Note:
The minimum thread stack size is 16 kilobytes for ia32 platforms and 96 kilobytes for ia64 platforms. If -Xss is set below the minimum value, thread stack size will default to the minimum value automatically.

Default:
The default thread stack sizes are as follows:

  • win32: 64k
  • linux32: 128k
  • win64: 320k
  • linux64: 1M
 Tuning
-Xstrictfp Enables strict floating point arithmatics globally for all methods in all classes. This option is similar to the Java keyword strictfp. See the Java Langugae Specification for more details on strictfp.  
-Xverbose:[param1,param2,...] JRockit prints, to screen at startup and during run-time, specific information about the system. The information displayed depends on which parameter(s) you specify with the option:
  • codegen
  • cpuinfo
  • gc
  • gcpause
  • gcreport
  • load
  • memory
  • opt

For a description of these options, please refer to Starting and Configuring BEA JRockit.
 Configuration
-Xverboselog:<file> Logs verbose output to the specified file. N/A
-Xverbosetimestamp Forces a timestamp to print with each verbose information that is generated by the -Xverbose option. Configuration
-Xverify, -Xverify:[all | none] Performs a complete bytecode verification. Configuration
-XXaggressive Performs adaptive optimizations as early as possible in the Java application run. To do this, the bottleneck detector will run with a higher frequency from the start and then gradually lower its frequency. This options also tells BEA JRockit to use the available memory aggressively. N/A
-XXcompactratio Sets how much (measured in percentage) of the Java heap that will be compacted when BEA JRockit perfoms a garbage collection. N/A
-XXfullsystemgc Causes garbage collection of old space and full compaction whenever System.gc() is called. Soft references are also released. N/A
-XXhpm This option uses hardware performance counters instead of software sampling in the Hotspot detector, which drives optimizations. The hardware performance counters gives higher accuracy for the hot spots sampling with better performance. This option is available and supported on Itanium for Red Hat 4.0 and SuSE 9.0. N/A
-XXjra:[param1,param2,...] This command starts a JRA recording from the command line. Specify one or all of the following parameters:

  • delay
  • recordingtime
  • filename
  • sampletime
  • nativesamples
 Using BEA JRockit Runtime Analyzer
-XXlargeObjectLimit This flag specifies the limit for when objects are treated as large objects. This value can be specified in kilobytes (K,k), megabytes (M,m), or gigabytes (G,g).

Default:
The default value is 2k.

N/A
-XXlargepages Tries to map large pages in the physical memory for the virutal memory used by JRockit. N/A
-XXminblocksize This size sets the smallest memory area that will be returned to the freelist and how large the thread-local area (TLA) will be. By consequence, this option sets the smallest available chunk of memory on the freelists. N/A