There are a variety of ways to obtain a dump from the IBM software development kit and various formats for the dump produced. It important to understand the content of each of the dumps so that the correct one can be selected for analysis of a given problem. In essence there are three forms of dump:
Dumps are produced by the JVM either on demand (a signal from the user) or on event (something happening within the VM). When the JVM starts it registers a number of event handlers which cause dumps to be generated for a default set of events. In the case of an Out of Memory event a heap dump is generated, for a user signal a javacore is generated and for a JVM crash a system dump is generated. For detailed information on setting the JVM options that control dump production see the IBM software development kit Diagnosis Guide or access this information through the IBM Support Assistant's Find Information activity.
When a system dump is produced by the JVM it is generated in a machine specific format and the internal structure of the information is specific to the VM that created it. To make the dump readable on other systems it is necessary to run the jextract program on the dump. Jextract is shiped as part of the IBM software development kit and can be run by passing the system dump as an argument, for example