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

Using dump agents

Dump agents are set up during JVM initialization. They enable you to use events occurring in the JVM, such as Garbage Collection, thread start, or JVM termination, to initiate dumps or to start an external tool.

The default dump agents are sufficient for most cases. Use the -Xdump option to add and remove dump agents for various JVM events, update default dump settings (such as the dump name), and limit the number of dumps that are produced.

• Using the -Xdump option
  The -Xdump option controls the way you use dump agents and dumps.
• Dump agents
  A dump agent performs diagnostic tasks when triggered. Most dump agents save information on the state of the JVM for later analysis. The "tool" agent can be used to trigger interactive diagnostic data.
• Dump events
  Dump agents are triggered by events occurring during JVM operation.
• Advanced control of dump agents
  Options are available to give you more control over dump agent behavior.
• Dump agent tokens
  Use tokens to add context to dump file names and to pass command-line arguments to the tool agent.
• Default dump agents
  The JVM adds a set of dump agents by default during its initialization. You can override this set of dump agents using -Xdump on the command line.
• Removing dump agents
  You can remove all default dump agents and any preceding dump options by using -Xdump:none.
• Dump agent environment variables
  The -Xdump option on the command line is the preferred method for producing dumps for cases where the default settings are not enough. You can also produce dumps using the JAVA_DUMP_OPTS environment variable.
• Signal mappings
  The signals used in the JAVA_DUMP_OPTS environment variable map to multiple operating system signals.
• Platform specifics
  Dump output is written to different files, depending on the type of the dump. File names include a time stamp.
• Disabling dump agents with -Xrs and -Xrs:sync
  When using a debugger such as GDB or WinDbg to diagnose problems in JNI code, you might want to disable the signal handler of the Java™ runtime environment so that any signals received are handled by the operating system.

Parent: Using diagnostic tools

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