I was surprised when I hit full GC because the tenured generation at only 37% in use, until I realized that I had been running for an hour. It was the sun.rmi.dgc.client/server.gcInterval settings - they are set to run full GC every hour. You do not want to manually force a collection - that could cause performance problems. Eventually, your tenured generation will fill up and you will hit a full collection. Even without a full collection, the JVM will occasionally free classes that are no longer used, thus reducing the size of the permgen. Set the -XX:+TraceClassUnloading option to see this. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4172430#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...