IBM User Guide for Java V7 on Windows > Troubleshooting and support > Using diagnostic tools > Tracing Java applications and the JVM

Controlling the trace

You have several ways by which you can control the trace.

You can control the trace in several ways by using:

• The -Xtrace options when launching the JVM, including trace trigger events
• A trace properties file
• com.ibm.jvm.Trace API
• JVMTI and JVMRI from an external agent

Note:

1. The specification of trace options is cumulative. Multiple -Xtrace options are accepted on the command line and they are processed in order starting with the option that is closest to the -Xtrace string. Each option adds to the previous options (and to the default options), as if they had all been specified in one long comma-separated list in a single option. This cumulative specification is consistent with the related -Xdump option processing.
2. By default, trace options equivalent to the following command parameter are enabled:

   -Xtrace:maximal=all{level1},exception=j9mm{gclogger}

3. To disable the defaults, use the -Xtrace:none option.
4. Many diagnostic tools start a JVM. When using the IBM_JAVA_OPTIONS environment variable trace to a file, starting a diagnostic tool might overwrite the trace data generated from your application. Use the command-line tracing options or add %d, %p or %t to the trace file name to prevent this from happening. See Detailed descriptions of trace options for the appropriate trace option description.

• Specifying trace options
  The preferred way to control trace is through trace options that you specify by using the -Xtrace option on the launcher command line, or by using the IBM_JAVA_OPTIONS environment variable.
• Detailed descriptions of trace options
  The options are processed in the sequence in which they are described here.
• Using the Java API
  You can dynamically control trace in a number of ways from a Java application by using the com.ibm.jvm.Trace class.

Parent: Tracing Java applications and the JVM

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