IBM User Guide for Java V7 on Windows > Troubleshooting and support > Using diagnostic tools > Using dump agents > Advanced control of dump agents

request option

Use the request option to ask the JVM to prepare the state before starting the dump agent.

The available options are listed in the following table:

Option value	Description
exclusive	Request exclusive access to the JVM.
compact	Run garbage collection. This option removes all unreachable objects from the heap before the dump is generated.
prepwalk	Prepare the heap for walking. You must also specify exclusive when using this option.
serial	Suspend other dumps until this one has finished.
preempt	Applies to the Javaâ„¢ dump agent and controls whether native threads in the process are forcibly pre-empted in order to collect stack traces. If this option is not specified, only Java stack traces are collected in the Javadump.

For example, the default setting of the request option for javadumps is request=exclusive+preempt. To change the settings so that javadumps are produced without pre-empting threads to collect native stack traces, use the following option:

-Xdump:java:request=exclusive

In general, the default request options are sufficient.

You can specify more than one request option using +. For example:

-Xdump:heap:request=exclusive+compact+prepwalk

Parent: Advanced control of dump agents

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