hi Adrian, Thanks for your respose. Our problem is that we are running a cluster - this problem just happens with the second node of the cluster - the mdb/pool from the first loaded server connects fine, but the second loaded server gives that client id message. We could solve the issue with a hand from Brian Stanberry, giving a login/client id on the jboss command line. But although it fixes the problem, it seems a horrible solution. Analysing your answer, as the mdb is not a ha-singleton, it is loaded on both servers. Then, either if we put the pool size to one, we will have one connection on each server which will bring the same issue. I understood that if we remove the client-id it will work fine. The client-id configuration is not necessary? Thank in advance. Regards, Marcelo View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4151494#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...