Set JVM Heap Size

Performance Tuning Guide provides some proposals for JVM Max Heap and Initial Heap

Must be set on Deployment Manager, Nodeagents and Application Servers

By default the heap sizes are set as follows:

  • Small deployment: Maximum Heap Size – 2506 MB
  • Medium deployment: Maximum Heap Size – 2506 MB
  • Large deployment: Each application in a Large deployment, except News and Search, has a default Heap size of 256 MB. The News and Search applications have a default Heap size of 784 MB.

You can monitor through Verbose Garbage Collection

Setting the minHeap = maxHeap can increase performance up to 10%

This article Tuning WebSphere Application Server V7 and V8 for performance from the WebSphere Tech Journal, is a good overview explaining the different pieced of performance tuning – http://www.ibm.com/developerworks/websphere/techjournal/0909_blythe/0909_blythe.html