Ok, looking a bit closer what I think you are asking is where JBoss gets the Oracle specific driver classes from. Typically you place this in your server/lib directory and it is available server wide. If another application is using a different version of those classes, or contains these classes as part of another application deployment you will receive a ClassCastException. More on this can be found here: http://wiki.jboss.org/wiki/Wiki.jsp?page=IWantToDeployMyOwnJdbcDriverInAS... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4039946#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...