This technology is a diagnostic tool for optimizing parameters affecting the garbage collector when using the IBM Java™ Virtual Machine (JVM). Applications running under Java use what is known as a Java heap for garbage collection, which serves as a storage manager in IBM's Java development kits and run-time environments.

An analysis of data reflecting the activity of the garbage collector in Java enterprise or stand-alone applications is critical to optimizing tasks running under a JVM. For example, issues such as the frequency of the garbage collection cycle, the time spent in different phases of the garbage collection, the quantities of heap memory involved in the process, the characteristics of the allocation failures from which the garbage collection originate, and the unwanted presence of stack overflows must be considered in optimization of parameters for Java applications and prevention of bottlenecks.

How does it work?

Diagnostic Tool for Java Garbage Collector helps to examine the characteristics of the garbage collection for an application running under a JVM by reading the output of the "verbose" garbage collection and producing textual and graphical visualizations and related statistics. This tool is particularly well suited for looking at the garbage collector activity of a heavily-accessed enterprise application hosted by a WebSphere® Application Server. The tool includes a "multiple file analysis" modality that allows the loading of two or more files simultaneously, thereby enabling the comparison of the behaviour of two or more application servers in a WebSphere cluster.

Diagnostic Tool for Java Garbage Collector 1.3 comes with three built-in parsers for IBM JVM 1.5.0, IBM JVM 1.4.2, and IBM JVM 1.2.2, as well as sample files for evaluating features of the tool and detailed documentation. Each parser is likely to be able to parse the data produced by some other versions of the IBM JVM; for instance, the JVM 1.4.2 parser also works well with the JVM 1.3.x. For unsupported versions of the IBM JVM, the tool contains detailed documentation that allows one to code a different parser in Java by implementing the GCParser interface. The documentation describes in detail the assumptions and the rules necessary for coding of the new parser.

Sergio Imperato is an IBM Certified Consulting IT Architect. He achieved his degree in Mechanical Engineering with full marks and honours in 1982. After working for a major Italian automotive company, Mr. Imperato joined IBM, where he currently works as an IT Consulting Architect in IBM Global Services, Business Consulting Services, and Travel and Transportation Industries.