JVM tuning

Key JVM

-Xmx                           -Xmx2G    maximum size of java heap.
-Xms                           -Xms1G     minimum size of java heap.
-server/client                 defines type of jvm
-d32/-d64                     specify the type of JVM
-XX:+NewRatio           -XX:+NewRatio=12     only 1/12 of the heap will be reserved for short-lived objects.
-XX:+UseParallelGC    use multi-cores or processor to do garbage collection in parallel or not.
-XX:+UseParallelOldGC