Don't use HSQL. If you are sending a lot of messages to your queues, and they become full and paging starts occurring, then JBM will start paging to the database. If you are using HSQL, then that "database" is in memory! So you're just going to get an OOM sooner or later. Your "pauses" are probably just long gc pauses as the JVM tries to regain memory as it nears the limit. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4052160#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...