This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
You need to track what the garbage collector is doing. See my paper at ceCMG for one way you could do this. (And no, using JConsole does not provide the necessary information - you need to know how much heap space is in use after each major collection.)