Java Stand-alone Applications on z/OS, Volume I

Chapter 7. Problem determination 193

identify otherwise hard to spot problems resulting from failing operations such as

pthread_quiesce_and_get_np( ) that are used to freeze threads prior to a GC. It

can be extracted from SVCDUMP using a tool such as svcdump.jar.

Other information such as debugging messages written to stderr by JVM or

debugging messages from your Java application can also help identify

application-specific problems. However, that is not our focus in this chapter.

Some problem determination data can be obtained from a profiling tool such as

the profiling tools in IBM Rational Application Developer Version 6 or the JDK

profiling tool Hprof. However, they are not as reliable as HEAPDUMP and the

performance impact prevents them from being used in a production environment.

7.4 Dump analysis and tools

This section describes the analysis of the following dumps:

򐂰 SYSTDUMP and SVCDUMP

򐂰 JAVADUMP

򐂰 HEAPDUMP

It also discusses tools such as svcdump.jar and HeapAnalyzer.

A simple Java program is used in this section to generate dumps on z/OS. The

program just keeps on creating new objects within an infinite loop until the Java

heap is exhausted. The Java heap size is set to 16M to reduce the dump size.

The default JAVA_DUMP_OPTS is used. Therefore, three dumps are generated

(Figure 7-1 on page 194).