In MySQL, the parent token is not propagated under either READ UNCOMMITTED, READ COMMITTED or REPEATABLE READ. I did not try SERIALIZABLE, but as mteira mentions, the higher the isolation level, the more likely each thread will read stale data, causing the join to fail. I think the problem lies in not acquiring a write lock on a token loaded for update from the beginning. This would prevent other tokens from reading it in databases that support the READ COMMITTED level. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3972746#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...