WebSphere Application Server V6: Web Server Plug-In Problem Determination

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This Article describes the techniques for diagnosing problems that are related to the Web server plug-in for WebSphere Application Server V6, including those resulting from configuration errors. The Web server plug-ins handle communications between a Web server and the Web container in an application server or servers. The Web server plug-in works with six different Web servers. However, this paper concentrates on the IBM HTTP Server and its plug-in. It does not address Web server problems or problems that are related to the application server Web container. 

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How to Resolve Memory Leak Problems in a Websphere? |Memory leak detection and analysis in WebSphere Application Server

There are four common categories of memory usage problems in Java:

• Java heap memory leaks
• Heap fragmentation
• Insufficient memory resources
• Native memory leaks

The common causes for Java heap memory leaks are:

• Insertion without deletion into collections
• Unbounded caches
• Un-invoked listener methods
• Infinite loops
• Too many session objects
• Poorly written custom data structures.

Memory usage problems due to insufficient memory resources can be caused by:

• Configuration issues (allocating too little memory for heap).
• System capacity issues(too little physical memory).

Native memory leaks are memory leaks in non-Java cod, for example:

• Type-II JDBC drivers
• fragmentation in the non-heap segment of the Java process's address space.

WebSphere Application Server and higher provides a two-stage solution for detection and analysis of memory leaks

• In the first stage, a lightweight memory leak detection mechanism running within the production WebSphere Application Server uses inexpensive, universally available Java heap usage statistics to monitor memory usage trends, and provides early notification of memory leaks. An automated heap dump generation facility (available in WebSphere Application Server running on IBM JDKs)generates multiple heap dumps that have been coordinated with sufficient memory leakage to facilitate comparative analysis using MDD4J.
• The second stagethe Memory Dump Diagnostic for Java (MDD4J) is used to analyze heap dumps outside the production application server

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