Diagnostic component

Diagnostic tools and data
Scenarios in which dump files might not be produced
Generating dumps with dump agents
Using Javadump
Using Heapdump
Using system dumps and the dump viewer
Tracing Java applications
Diagnosing class-loading issues

Diagnostic tools and data
The J9 virtual machine (VM) produces various types of diagnostic information for analysis. A range of tools can be used to post-process this information and help with problem determination.
Scenarios in which dump files might not be produced
In certain scenarios, a dump is not produced when a crash occurs. This section gives reasons why a dump file is not produced and suggests how you can obtain a system dump file.
Using dump agents
Dump agents are set up during the initialization of the Java virtual machine. Dump agents enable you to use events occurring in the Java virtual machine (VM), such as garbage collection, thread start, or VM termination, to initiate dumps or to start an external tool.
Using Javadump
Java dumps are produced automatically when the VM ends unexpectedly, capturing diagnostic data about the VM and the Java application that was running. You can also trigger the production of a Java dump by calling the Dump API or specifying the -Xdump:java option on the command line.
Using Heapdump
The term Heapdump describes the JVM mechanism that generates a dump of all the live objects that are on the Java heap, which are being used by the running Java application.
Using system dumps and the dump viewer
The JVM can generate native system dumps, also known as core dumps, under configurable conditions.
Tracing Java applications
JVM trace is a trace facility that is provided in the J9 JVM with minimal affect on performance. Trace data can be output in human-readable or in compressed binary formats. The JVM provides a tool to process and convert the compressed binary data and into a readable format.
Diagnosing class-loading issues
To diagnose problems with class-loading, you can run a number of command line options and trace class-loading activity. If loading native libraries for a class, problems can exist with class paths.