Taken from the IBM Public Library for Websphere 4.x (a little out-dated). In this featured article for WebSphere 4.x, the concept is applicable to most J2EE application in determining if java.lang.OutOfMemoryError is due to allocation of large heap objects which is the cause of heap fragmentation. Heap fragmentation can be detected when there is a (a) high amount of free heap and a (b) high amount of memory in heap while a (c) "totally out of heap space message" occur. Techniques on how to resolve the problem such as coding it to prevent heap fragmentation, diminishing the effect of potential heap fragmentation are discussed in the article, etc. To get the article, click on the following link:

• WASJDK: java.lang.OutOfMemoryError due to allocating large heap objects

For the latest version of the WebShere documentation and tuning guide, you can refer to the IBM Public Library for WebSphere 6.x where there are various resources for performance tuning WebSphere 6.x.

(Special thanks to Aravind Kumar for contribution, CSS Corp)