Problems to tackle with the dump viewer

Dumps of JVM processes can arise either when you use the -Xdump option on the command line or when the JVM is not in control (such as user-initiated dumps).

The extent to which jextract can analyze the information in a dump is affected by the state of the JVM when it was taken. For example, the dump could have been taken while the JVM was in an inconsistent state. The exclusive and prepwalk dump options ensure that the JVM (and the Java™ heap) is in a safe state before taking a system dump:
-Xdump:system:defaults:request=exclusive+prepwalk
Setting this option adds a significant performance reduction when taking a system dump; which could cause problems in rare situations. This option is not enabled by default.

jdmpview is most useful in diagnosing customer-type problems and problems with the class libraries. A typical scenario is OutOfMemoryError exceptions in customer applications.

For problems involving gpfs, ABENDS, SIGSEVs, and similar problems, you will obtain more information by using a system debugger (gdb) with the dump file. The syntax for the gdb command is
gdb <full_java_path> <system_dump_file>
For example:
gdb /sdk/jre/bin/java core.20060808.173312.9702.dmp

jdmpview can still provide useful information when used alone. Because jdmpview allows you to observe stacks and objects, the tool enables introspection into a Java program in the same way as a Java debugger. It allows you to examine objects, follow reference chains and observe Java stack contents. The main difference (other than the user interface) is that the program state is frozen; thus no stepping can occur. However, this allows you to take periodic program snapshots and perform analysis to see what is happening at different times.



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