I suspect your problem arises from using a Synchronization to update JBC. JBC itself uses a Synchronization to control replication of transactional changes around the cluster. If your Synchronization's beforeCompletion is executed by the TransactionManager after JBC's, I'm not sure what will happen. Are you able to ensure that your Synchronization is registered with the transaction before any call goes into JBC? I'm not sure from your original post -- do you see this with both pessimistic and optimistic locking? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3995664#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...