"timfox" wrote : | Interestingly the same problem occurs with BMT as well even though no transaction should have been started at all. BMT doesn't count as an "unspecified tx context" so the reasoning for starting a tx there shouldn't apply as it does for CMT. Hmmm, it seems that if I omit the acknowledge-mode from the MDB deployment descriptor when using BMT, then it defaults to transacted. This seems to be in contravention to the EJB spec: 15.4.8 anonymous wrote : | If the acknowledge-mode deployment | descriptor element is not specified, JMS AUTO_ACKNOWLEDGE semantics are assumed. | This would explain the above behaviour: The JCA adaptor is creating an xasession on the xaconnection even though it's BMT (and should be auto_ack since I haven't specified acknowledge-mode), then trying to call commit on it at the end. Instead, it should be creating a non transacted session, on a non xa connection and not calling commit at the end since it's non transacted. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4001333#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...