6.2 Choosing a garbage collection policy
There are four garbage collection policies available in the Java 5 IBM JVM.
The four GC policies available in the IBM JVM are:
- Optimal Throughput
- Optimal Average Pause
- Generational Concurrent
- Subpool
The default GC policy is Optimal Throughput.
This is most likely not the best choice. Because throughput is the goal for this policy, longer pauses during garbage collection can be expected. The two policies better suited for WebSphere Application Server applications are Generational Concurrent and Subpool. Generational Concurrent was designed with the typical characteristics of WebSphere applications in mind, and Subpool takes advantage of AIX and System p hardware features.
The four GC policies are explained in greater detail in other sections of this chapter. Some policies require additional manual tuning. Because the tuning parameters require knowledge of GC internals, a brief explanation of Java memory management is provided next.