Did you then configure DefaultDS to use MySQL? There is no reason that you cannot use both Hypersonic and MySQL. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4034120#4034120 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4034120