When out of memory

Enable the JVM's ability to dump the heap upon error and then analyze it with IBM HeapAnalyzer or Eclipse MAT.  To do so, add +-XX:+HeapDumpOnOutOfMemoryError to the JVM parameter line (or use jmap to force a heap dump if you know when it's close to dying).

+

You can also enable verbose GC logging to get a better sense of what the heap is doing:

-verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails -XX:+PrintTenuringDistribution -Xloggc:<gc-log-location.log>