Heap dumps contain a snapshot of all the live objects that are being used by a running Java application on the Java heap. There are two formats for heap dumps; the classic format, which is ascii text and the PHD format, which is compressed and not readable.
A heap dump contains a list of all object instances. For each object instance you can find the following additional data:
- The object address
- The type or class name
- The size
- Any references to other objects
For a visual analysis of a heap dump as an aid to problem determination, use the Eclipse Memory Analyzer tool (MAT) or the IBM Memory Analyzer tool. Both tools require the Diagnostic Tool Framework for Java (DTFJ) plugin. To install the DTFJ plugin in the Eclipse IDE, select the following menu items:
Help > Install New Software > Work with "IBM Diagnostic Tool Framework for Java" > IBM Monitoring and Diagnostic Tools > Diagnostic Tool Framework for Java
For more information about using the Heapdump feature, see Using Heapdump.