First, there are several variations of out-of-memory errors and each one has a different solution. Exactly what error are you seeing? If you are getting an "out of heap space" error with only 10 users, then you are either working with large data items (can happen is you load large XML documents) or you have a memory leak. If you have a memory leak then increasing the heap size will not help. Having a large heap is not always a good thing - the larger the heap the longer it will take to do a full garbage collection. You really need to analyze the heap usage of your program. Search for some of my posts in the performance tuning forums for suggestions. Also see my presentation at http://www.cecmg.de/doc/tagung_2007/agenda07/24-mai/2b3-peter-johnson/ind... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4205662#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...