Tuning Garbage Collection with JRockit

Monitoring and Troubleshooting 8-31 For replica servers, increase the available memory: -Xms3072m -Xmx3072m -XgcPrio:deterministic -XpauseTarget=30ms -XXtlasize:min=8k -XXnosystemgc These settings fix the heap size and enable the dynamic garbage collector with deterministic garbage collection. -XpauseTarget sets the maximum pause time and -XXtlasize=3k sets the thread-local area size. -XXnosystemgc prevents System.gc application calls from forcing garbage collection.

8.8.4 Using Oracle JRockit without Deterministic Garbage Collection

When using Oracles JRockit JVM without deterministic garbage collection not recommended for production deployments, the best response time performance is obtained by using the generational concurrent garbage collector. The full list of example startup options for an engine tier server are: -Xms1024m -Xmx1024m -Xgc:gencon -XXnosystemgc -XXtlasize:min=3k -XXkeeparearatio=0 -Xns:48m The full list of example startup options for a replica server are: -Xms3072m -Xmx3072m -Xgc:gencon -XXnosystemgc -XXtlasize:min=3k -XXkeeparearatio=0 -Xns:48m

8.8.5 Tuning Garbage Collection with Sun JDK

When using Suns JDK, the goal in tuning garbage collection performance is to reduce the time required to perform a full garbage collection cycle. You should not attempt to tune the JVM to minimize the frequency of full garbage collections, because this generally results in an eventual forced garbage collection cycle that may take up to several full seconds to complete. The simplest and most reliable way to achieve short garbage collection times over the lifetime of a production server is to use a fixed heap size with the default collector and the parallel young generation collector, restricting the new generation size to at most one third of the overall heap. The following example JVM settings are recommended for most engine tier servers: -server -Xmx1024m -XX:MaxPermSize=128m -XX:+UseParNewGC -XX:+UseConcMarkSweepGC Note: The above settings are configured by default in the WLSS_ HOMEcommonbinwlssCommenv.sh file when you use the Configuration Wizard to create a new domain with the JRockit JVM. You may need to increase the -XpauseTarget value for allocation-intensive applications. The value can be decreased for smaller applications under light loads. Adjust the heap size according to the amount of live data used by deployed applications. As a starting point, set the heap size from 2 to 3 times the amount required by your applications. A value closer to 3 times the required amount generally yields the best performance. Note: Fine tune the heap size according to the amount of live data used by deployed applications.