GCMON is an agent tool to gather performance statistics of JVM runtime informations, and log     out them to a file or standard output stream as specified by the command line options.      As a result, GCMON will make a file, record the snapshot of system memory usage and each generation's     space of JVM when the OutOfMemroyError exception occurs, finally it will send a diagnostic message to     the user, and calculate a suggestion based on those informations.