"timfox" wrote : Furthermore - we should ensure there is zero overlap between any other 1.x and 2.x class names as this may cause other subtle issues when running both sets of classes in the same classloader. Can't we rename the whole base package? (org.jboss.messaging to something else?) I have been there when we had to play with SAR isolations and it wasn't any fun. I foresee users using both JBM 1.4 and JBM 2.0 on the same VM during migrations... and it would be better to be completely isolated. We could verify of course if there are no clashes.. but if renaming the package is acceptable.. that would give some peace of mind. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4201469#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...