Change the default heap size of JRockit JVM

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To change the default heap size go to your <WebLogic Home>\user_projects\domains\soa_domain\bin\setSOADomainEnv.sh or .cmd and modify the values of PORT_MEM_ARGS=-Xms768m –Xmx1536m.

By default it looks like

set PORT_MEM_ARGS=-Xms768m -Xmx1536m

I have modified it to

set PORT_MEM_ARGS=-Xms6144m -Xmx6144m –Xns2048m

-Xms sets the initial size of the heap. For SOA, its recommend to set it to the same size as the maximum heap size

-Xmx sets the maximum size of the heap.

-Xns sets the size of the young generation (nursery) in generational concurrent (-Xgc:gencon) and generational copying garbage collectors (-Xgc:gencopy)

If the nursery size (-Xns) has not been set the default size depends on the type of garbage collector and the number of CPUs:

  • For the generational copying garbage collector (-Xgc:gencopy) the default nursery size is 320 KB per CPU; for example, the default for a ten CPU system using gencopy would be 3200 KB (3.2 MB).
  • For the generational concurrent garbage collector (-Xgc:gencon) the default nursery size is 10 MB per CPU; for example, the default for a ten CPU system using gencon would be 100 MB.

Some good readings on JVM

Why is my JVM process larger than max heap size https://blogs.oracle.com/jrockit/entry/why_is_my_jvm_process_larger_t

Is a JVM's Maximum Heap Size really 1.7 GB?

http://pauldone.blogspot.com.au/2008/08/is-jvms-maximum-heap-size-really-17-gb.html

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