Actually I'm not sure it would. The physical and logical connections are both in the same autocommit state (FALSE) at the time of the set transaction isolation call. Inbetween, the logical connection had autocommit TRUE but this was not applied to the physical connection at the time because no other methods were called on the connection whilst it was logically in this state. If the connection has not been committed or rolled back explicitly, then a newly returned connection could be part of an old transaction, I think. Is there a reason why set autocommit is not passed down to the physical connection immediately but instead checked on every other call and passed down then? The more I think about this the more I think such a fundamental mistake probably wasn't made and my interpretation is wrong.. but I'd love it if someone could put my mind to rest! View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4236932#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...