It seems that I have hit the same problem. Oracle 10.2.0.3 (3 nodes RAC cluster) RedHat x86_64 2.6.9-34.ELsmp JBoss [Zion] 4.0.3SP1 There is no data replication of any kind in our database. When I connect JMS pool to the RAC service that is tied to one node then the problem does not occur. When I let it run on three nodes then the exception occurs for a small percentage of the messages. Our effects are the same if we run JBoss clustered or on a single node. There is a difference in the behavior only if I let the pool run on one node or three nodes. I have been looking on the internet for more information with no results. Please post anything useful if you can. Regards, AnT View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4069062#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...