I have a production server running with the following flag: -XX:+HeapDumpOnOutOfMemoryError
Last night it generated a java-38942.hprof file when our server encountered a heap error. It turns out that the developers of the system knew of the flag but no way to get any useful information from it.
Any ideas?
You can use JHAT, The Java Heap Analysis Tool provided by default with the JDK. It's command line but starts a web server/browser you use to examine the memory. Not the most user friendly, but at least it's already installed most places you'll go. A very useful view is the "heap histogram" link at the very bottom.
ex: jhat -port 7401 -J-Xmx4G dump.hprof
jhat can execute OQL "these days" as well (bottom link "execute OQL")