Issue 1: We have a cluster of 2 nodes with MDBs deployed in /jboss-4.0.5.GA/server/all/deploy, let's call the servers M1 and M2. They are listening on another cluster of 2 nodes hosting a JBossMQ queue, let's call them Q1 and Q2. So, there are 4 total Jboss AS running concurrently, M1, M2, Q1 and Q2. 1 JMS msg was put on the queue on Q1, the master node . Both MDBs, M1 and M2 consumed the same message and applied their business logic. How is that possible that 2 MDBs consumed the same JMS message? I thought either one of M1 or M2 would consume JMS, but not both. In our setup, only one MDB has to do work. Is it possible to put the MDBs (ear file) on M1 and M2 in jboss-4.0.5.GA/server/all/deploy-hasingleton to act in singleton mode or are there other solutions? Issue 2: I copied ear file containing the MDB into deploy-hasingleton dir. 1) started M1 and M2, ear deployed in M1, but not M2 as expected 2) after shutting down M1, M2 does not become master (problem) Is there anything else I have to configure to get ear file to work as a singleton? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4124866#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...