Monitor CICS JVM Server using IBM Support Assistant

Memory leaks from Java programs can have serious consequences as well as memory leaks from other non-Java language programs. Although Java has a garbage collector, referenced objects can sometimes be reclaimed by the garbage collector. Therefore, to resolve memory leaks in Java programs, you first need to locate the memory leak and then identify the class that is causing the memory leak. This article takes a sample Java program running on the CICS JVM server to show how to locate the memory leak and identify the class that is causing the memory leak.

Introduced

Memory management is one of the advantages of Java. When the memory of objects created in the Java language is no longer needed, the garbage collector (GC) will reuse the memory, which makes memory management simple. However, even with the garbage collector, Java programs can generate memory leaks if no references to objects are removed after use. A memory leak can occur when a program creates a reference to an object without releasing the references. A typical example is to add objects to a Java collection (collection), and if you do not delete references to those objects after processing, you can cause an increasing number of unwanted object references in your application.

After a program is started, the amount of heap usage is generally constant. As more and more objects are created, the amount of space in the heap becomes more and more, so the usage of the heap increases. The GC reclaims the space occupied by objects that are no longer needed. When a Java program begins to leak memory, the amount of heap usage increases because the object is created and cannot be purged by GC, resulting in Java.lang.OutOfMemoryError.

Use this article to run at IBM? A sample Java program that causes memory leaks in the CICS JVM server shows you how to use the two tools of IBM Support Assistant (ISA).

ISA Introduction

For all IBM software users, ISA is a free tool that provides support and maintenance. In addition, it provides a working platform that can be used with other problem-locating tools to help with the problem positioning. Download Isa and learn more about it.

After you download Isa, you can customize the Isa Workbench with a variety of different tools, depending on your needs. This article focuses on two tools-Health Center and Memory Analyzer. To add both tools, on the ISA Workbench home page, click the Analyze Issues button, click the Find new tool add-ons link, and then select the check boxes for the following two items:

IBM Monitoring and diagnostic Tools for Java-Health Center

IBM Monitoring and diagnostic Tools for java–memory Analyzer

Follow the instructions for the Installation Wizard to install and restart Isa as prompted.

Connect Health Center

Modify the JVM configuration file for the JVM server. Add the-xhealthcenter option to the profile, disable (disable) the JVM server, and then enable the JVM server resource for the configuration to take effect.

Set the listening port for the Health center agent. To locate its listening port, view the Dfhjvmerr file in the directory specified by the WORK_DIR option in the configuration file for your JVM server. Find the following line of text in the Dfhjvmerr file to find the port you should be connecting to:

Info:health Center agent started on port 1972.

Start Isa and click the analysis issue (Analyze Problem) on the home page to connect to Health Center. From the list of installation tools, select Health Center, and follow the wizard's instructions to enter the host name and port. After you complete the steps specified by the wizard, Health Center connects to your JVM server and starts collecting monitoring data.