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

Tracing Java applications and the JVM

JVM trace is a trace facility that is provided in all IBM-supplied JVMs with minimal affect on performance. In most cases, the trace data is kept in a compact binary format, that can be formatted with the Java™ formatter that is supplied.

Tracing is enabled by default, together with a small set of trace points going to memory buffers. You can enable tracepoints at run time by using levels, components, group names, or individual tracepoint identifiers.

Trace is a powerful tool to help you diagnose the JVM.

• What can be traced?
  You can trace JVM internals, applications, and Java method or any combination of those.
• Types of tracepoint
  There are two types of tracepoints inside the JVM: regular and auxiliary.
• Default tracing
  
• Where does the data go?
  Trace data can be written to a number of locations.
• Controlling the trace
  You have several ways by which you can control the trace.
• Using the trace formatter
  The trace formatter is a Java program that converts binary trace point data in a trace file to a readable form. The formatter requires the J9TraceFormat.dat file, which contains the formatting templates. The formatter produces a file containing header information about the JVM that produced the binary trace file, a list of threads for which trace points were produced, and the formatted trace points with their timestamp, thread ID, trace point ID and trace point data.
• Determining the tracepoint ID of a tracepoint
  Throughout the code that makes up the JVM, there are numerous tracepoints. Each tracepoint maps to a unique id consisting of the name of the component containing the tracepoint, followed by a period (".") and then the numeric identifier of the tracepoint.
• Application trace
  Application trace allows you to trace Java applications using the JVM trace facility.
• Using method trace
  Method trace is a powerful tool for tracing methods in any Java code.

Parent: Using diagnostic tools

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