I have had to deal with memory problems in Java applications a few times. A lot has been written about this already, but this time I ran into a slightly different issue that surprised some of my colleagues so I decided to write about it here. Contrary to popular belief, a big JVM heap size is not always better when it comes to performance.
The problem
I came to the customer site to help them with their performance problems of a fairly large J2EE-system Web Service/Hibernate/MySQL system. They had several customers running the system, but only the largest was experiencing problems. The application suddenly froze and stopped processing transactions. All sorts of hypotheses were discussed, but no one could really for sure say what the problem was. And there was little data to work on.