I just took a look at the tx management code in the JCA adapter, and it looks just plain wrong in places. JBMMessageHandler::onMessage. Firstly it seems a transaction is *always* being started and committed/rolled back for *every* message. It's my understanding that this should only be done if the bean is using CMT and the transaction atttribute is Required. For BMT or transaction attribute=NOT_SUPPORTED no transaction should be created. Also | if (activation.getActivationSpec().getAcknowledgeModeInt() == Session.SESSION_TRANSACTED || activation.getActivationSpec() | .getAcknowledgeModeInt() == Session.CLIENT_ACKNOWLEDGE) | { | try | { | message.acknowledge(); | } | catch (MessagingException e) | { | log.error("Failed to process message", e); | } | } | The above code is a nonsense, since a) it's illegal to use CLIENT_ACKNOWLEDGE in a MDB and b) if a session is transacted, message.acknowledge() does nothing anyway. Also the code in JBMResourceAdapter::createSession seems just plain wrong - it seems to be creating XA sessions when ack mode = auto_ack !! ?? The specification "EJB core contracts and requirements" Chapter 5 should be read properly and the code in the adapter corrected. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4244258#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...