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 generati...