20. Summary The JVM and JMX make a lot of information available The tools to get at the information are readily available All that you have to do is understand what it is telling you
21. Hot method Repeated Thread dumps reveals one method appears frequently It is either occuring a lot or running slowly
22. System.gc Frequent major garbage collections jstat shows a large GCT and System.gc as the previous GC cause VisualVM shows large proportion of CPU time spent garbage collecting