Hi! Its mee again. I spend arround 5 hours now digging in JBM code to find out why my system behaves as it does. Testenvironment: - One local persistent Queue with a lot of messages in. - An EJB3 MDB attached to the Queue using maxSession and maxMessages set to 1 - redelivery is set to MDBs default (5 think) - JBM 1.4.0 SP3 on 4.2.1 GA To test Logic errors and the ways JBM handles exceptions I set context.setRollbackOnly() while handling the messages in my MDB onMessage() method. What I thought is this behaviour of Message A B C....: A -> fail A -> fail A -> fail A -> fail A -> fail -> DLQ B -> fail B -> fail B -> fail B -> fail B -> fail -> DLQ and so on But what happens is always a handling of 2 messages: A -> fail B -> fail A -> fail B -> fail A -> fail B -> fail A -> fail B -> fail A -> fail -> DLQ B -> fail -> DLQ C -> fail D -> fail C -> fail D -> fail and so on... While debugging and tracing I see that the ClientConsumer calls removeFirst() on the BasicPriorityLinkedList from 2 Threads and in twisting manner the addFirst() and removeFirst() which lead in this A,B,A,B order. What can I do to have this AAAABBBB handling? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4159467#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...