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Tuning WebLogic JRockit 8.1 JVM

# Command Line Options by Name

This appendix lists the valid WebLogic JRockit JVM command line options in alphabetical order, by name.

Note: Options that begin with `-X` are non-standard options (called "`-X` options") and are subject to change at any time.

Table A-1 Command Line Options by Name

Option | Description
--- | ---
`-classpath -cp` | Tells WebLogic JRockit JVM where to look for classes and resources.
`-D` | Tells WebLogic JRockit JVM to set a Java system property. These can be read by a Java program, using the methods in `java.lang.System`.
`-help` | Tells WebLogic JRockit JVM to display a short help message.
`-showversion` | Tells WebLogic JRockit JVM to display its product version number and then continue with startup.
`-verbose -Xverbose` | Tells WebLogic JRockit JVM to display verbose output.
`-version` | Tells WebLogic JRockit JVM to display its product version number and then exit.
`-X` | Tells WebLogic JRockit JVM to display a short help message on the extended options.
`-Xallotype` `-Xallocationtype` | Sets the type of allocation. Parameters: `global`; global allocation `local`; thread local allocation For details on these options, please refer to Table 2-2 in Tuning the WebLogic JRockit JVM.
-Xbootclasspath | Sets the search path for bootstrap classes and resources. Specify the names of the directories, `.zip`, and `.jar` files, separated by ";" (Windows) or ":" (Linux).
`-Xcleartype` | Defines when the memory space occupied by an object that has been garbage collected will be cleared. The parameters listed below determine when the space is cleared. Parameters: `gc`; cleared during garbage collection `local`; cleared when a thread-local area is allocated `alloc`; cleared when that space is allocated for a new object For details on these options, please refer to Table 2-1 in Tuning the WebLogic JRockit JVM. Notes: The `-Xcleartype:local` option is available only if the `-Xallocationtype` is set to local. The `alloc` option is not available on IA64 systems.
`-Xgc` | Deploys the specified garbage collector. Parameters: `gencopy`; Generational Copying `singlecon`; Single Spaced Concurrent `gencon`; Generational Concurrent `parallel`; Parallel The default is `gencopy` if `-Xmx` is less than 128MB; otherwise, it's `gencon`.
`-Xgcpause` | Prints pause times caused by the garbage collector.
`-Xgcreport` | Causes WebLogic JRockit JVM to print a comprehensive garbage collection report at program completion. The option `-Xgcpause` causes the VM to print a line each time Java threads are stopped for garbage collection.
`-Xjvmpi` | Enables and disables groups of JVMPI events when running `JVMPI.` The events are: `entryexit` (default is ON) `allocs` (default ON) `monitors` (default (ON) `arenasdelete` (default OFF) Note: JVMPI is an experimental feature in the Java 2 SDK and is not yet a standard profiling interface.
`-Xmanagement` | Enables the management server in the VM, which needs to be started before the Management Console can connect to WebLogic JRockit JVM.
`-Xms` | Sets the initial size of the heap. You should set the initial heap size (`-Xms`) to the same size as the maximum heap size. The default is 16 MB if maximum heap size is limited to less than 128 MB, otherwise 25% of available physical memory, but not exceeding 64 MB. This value can be specified in kilobytes (`K`,`k`), megabytes (`M`,`m`), or gigabytes (`G`,`g`).
`-Xmx` | Sets the maximum size of the heap. You should set this value as high as possible, but not so high that it causes page-faults for the application or for some other application on the same computer. The default is the lesser of 75% of physical memory and 400 MB when running `gencopy`; when running another garbage collector, the default is the lesser of 75% of physical memory and 1536 MB. This value can be specified in kilobytes (`K`,`k`), megabytes (`M`,`m`), or gigabytes (`G`,`g`).
`-Xnativethreads` | Enables the Native Threads system. This option is the default, therefore you only need to specify it when you want to change the method from thin threads.
`-Xnoclassgc` | Disables class garbage collection.
`-Xnohup` | When specified, tells WebLogic JRockit JVM not to watch for or process `CTRL_LOGOFF_EVENT` or `SIGHUP` events.
`-Xnoopt` | Tells WebLogic JRockit JVM not to optimize code.
`-Xns` | Sets the size of the young generation (nursery) in generational concurrent and generational copying garbage collectors (these are the only collectors that use nurseries). If you are creating a lot of temporary objects you should have a large nursery. The default is default is 10 MB per CPU with a `gencon` garbage collector and 320 KB per CPU with `gencopy`. This value can be specified in kilobytes (`K`,`k`), megabytes (`M`,`m`), or gigabytes (`G`,`g`).
`-Xss` | Sets the thread stack size; can be specified in kilobytes (`K`,`k`), megabytes (`M`,`m`), or gigabytes (`G`,`g`).
`-Xthinthreads` | Implements the WebLogic JRockit High Performance Threading System (Thin Threads). This option is not available on IA64. Warning: Thin threads is experimental functionality in this version of WebLogic JRockit, and is not recommended for general use. This feature is subject to change without notice.
`-Xverbose` | Causes WebLogic JRockit to print to the screen, upon startup, specific information about the system. The information displayed depends upon the parameter specified with the one of these options: `codegen` `cpuinfo` `gc` `load` `memory` Opt For a description of these options, please refer to Table 3-1 in Starting and Configuring WebLogic JRockit.
`-Xverify` | Tells WebLogic JRockit JVM to do complete bytecode verification.