[WAS_7.0_INFOCENTER] Locating and analyzing heap dumps

Generating a Java heap dump

A Java heap dump is an IBM software development kit (SDK)-generated data file containing a snapshot of the current memory state of the application server JVM. A Java heap dump is generated automatically when the JVM runs out of memory.

To issue a command to generate a heap dump in wsadmin.sh, you must first obtain a reference to the message bean (MBean) that is associated with the JVM running in your process using the command that is shown below:

jvm = AdminControl.queryNames("WebSphere:type=JVM,process=server1,node=devNode,*")
AdminControl.invoke(jvm, 'generateHeapDump')					
					

Afterward, use the following command to induce the Java heap dump:

AdminControl.invoke(jvm, 'generateHeapDump');
					

Generating Java core dump

The Java core dump is a IBM SDK-generated data file, which contains information pertaining to the threads and monitors in the JVM. Just as the Java heap dump is a snapshot of the process JVM memory, the Java core dump is a snapshot of the threads running on the JVM. This data file is generated automatically every time that a server crashes. Or, a user can issue a command to generate this data file.

To issue a command to generate a core dump in wsadmin, you must first obtain a reference to the MBean that is associated with the JVM running in your process using the command shown below:

jvm = AdminControl.queryNames("WebSphere:type=JVM,process=server1,node=devNode,*")
AdminControl.invoke(jvm, 'dumpThreads')
					

Afterward, use the following command to start the Java core dump:

AdminControl.invoke(jvm, 'dumpThreads');
					

Locating and analyzing heap dumps

Do not analyze heap dumps on the WebSphere Application Server machine because analysis is very expensive. For analysis, transfer heap dumps to a dedicated problem determination machine.

When a memory leak is detected and heap dumps are generated, you must analyze heap dumps on a problem determination machine and not on the application server because the analysis is very central processing unit (CPU) and disk I/O intensive.

Perform the following procedure to locate the heap dump files: