Thanks John, Using a NUMBER as the PK is my preference as a rule but I've been asked to do it this way and I can see know reason, looking at the EJB3 spec, it shouldn't work. I find the differing behaviour depending on the transaction usage worrying and want to know if I should work around it (using a NUMBER column as you say) or am I doing something wrong or whether it's a bug? Cheers Tom Boswell View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3972623#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...