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

Using the -Xdump option

The -Xdump option controls the way you use dump agents and dumps.

You can use the -Xdump option to:

• Add and remove dump agents for various JVM events.
• Update default dump agent settings.
• Limit the number of dumps produced.
• Show dump agent help.

The syntax of the -Xdump option is as follows:

-Xdump command-line option syntax

>>--Xdump:--+-help----------------+----------------------------><
            +-none---:<options>---+   
            +-events--------------+   
            +-request-------------+   
            +-tokens--------------+   
            +-dynamic-------------+   
            +-nofailover----------+   
            +-what----------------+   
            '-<agent>:<options>---'   

You can have multiple -Xdump options on the command line. You can also have multiple dump types triggered by multiple events. For example, the following command line turns off all Heapdumps, and creates a dump agent that produces a Heapdump and a Javadump when either a vmstart or vmstop event occurs:

java -Xdump:heap:none -Xdump:heap+java:events=vmstart+vmstop <class> [args...]

You can use the -Xdump:what option to list the registered dump agents. The registered dump agents listed might be different to the agents you specified. The difference is because the JVM ensures that multiple -Xdump options are merged into a minimum set of dump agents.

The events keyword is used as the prime trigger mechanism. However, you can use additional keywords for further control of the dump produced.

The options that you can use with dump agents provide granular control. The following syntax applies:

-Xdump command-line agent option syntax

             .-+-------.                                               
             V         |                                               
>>--Xdump:-----<agent>-+-+---------------------------------------+---><
                         '-:-+-help----------------------------+-'     
                             +-none---:<options>---------------+       
                             +-defaults------------------------+       
                             | .-,---------------------------. |       
                             | |           .-+-----------.   | |       
                             | V           V             |   | |       
                             '---+-events=-----<event>---+-+-+-'       
                                 +-exec=<command>----------+           
                                 +-file=<filename>---------+           
                                 +-filter=<filter>---------+           
                                 +-opts=<options>----------+           
                                 +-priority=<0-999>--------+           
                                 +-range=<ranges>----------+           
                                 '-request=<requests>------'           

Help options

These options provide usage and configuration information for dumps, as shown in the following table:

Command	Result
-Xdump:help	Display general dump help
-Xdump:events	List available trigger events
-Xdump:request	List additional VM requests
-Xdump:tokens	List recognized label tokens
-Xdump:what	Show registered agents on startup
-Xdump:<agent>:help	Provides detailed dump agent help
-Xdump:<agent>:defaults	Provides default settings for this agent

• Merging -Xdump agents
  -Xdump agents are always merged internally by the JVM, as long as none of the agent settings conflict with each other.

Parent: Using dump agents

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