http://jcp.org/en/jsr/detail?id=220 The mechanism is explained in EJB 3 Persistence 3.4. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4061857#4061857 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4061857