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Working with SOA technologies , implementing solution using IBM BPM , IBM Integration Designer,IBM WODM and IBM DataPower

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Saturday, 13 October 2012

Increasing the JVM heap size in WAS7

Intensive use of WAS7 often slows down the server because of too often garbage collection. Most frequently this situation arises when WAS profile is augmented with at least two products, i.e. WPS and Monitor or WPS and Fabric. This situation can be avoided by increasing the JVM heap size. JVM heap size can be increased through administrative console or by using scripting.
In the administrative console click:
Servers > Server Types > WebSphere application servers >  SERVER_NAME > Server
Infrastructure > Java and process management  > Process definition > Java Virtual Machine

Set Maximum heap size field to desired value. Restart the server to bring in effect the value you set. Recommended value for maximum heap size by IBM is:
MaximumHeapSize = TotalRAM / 2 / NumberOfServers

JVM maximum heap size can be also set by scripting through wsadmin tool (heap size is in MB):
  • Jython:
AdminTask.setJVMMaxHeapSize('-serverName YOUR_SERVER_NAME
-nodeName YOUR_NODE_NAME -maximumHeapSize DESIRED_HEAP_SIZE')

  • JACL:
$AdminTask setJVMMaxHeapSize {-serverName YOUR_SERVER_NAME -nodeName YOUR_NODE_NAME -maximumHeapSize DESIRED_HEAP_SIZE}
In our experience 1536 MB is enough for testing purposes on WPS+Monitor or WPS+Fabric combinations.