A singleton MDB is triggered periodically by a timer. However, the timer thread which calls the ejbTimeout method seems to run concurrently with the thread which invokes the onMessage method, which destroys the singleton character of the MDB. Is there any means to guarantee that an MDB which runs on a timer behaves as a true singleton? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4134956#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...