If you used another persistence context, your objects would become detached when the persistence context ended. (either at the end of the transaction or when the associated session bean is removed, depending on the persistence context type) When that happens, you can notice a couple of problems. First, you would no longer be able to save changes to the entity into the database without manually merging it back into the new persistence context. You might also get lazy instantiation errors if you try to access state/relations that had not yet been loaded. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4000672#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...