They both support concurrency; it's just that optimistic locking will allow readers to read while writers write, allowing a *higher level* of concurrency. Regarding the deadlock with remote prepares, this is a possibility with both OL and PL, since remote locks are only acquired on prepare and not at the start of a transaction. Locks should be released after the transaction times out though; which forum thread are you referring to about this being reported as a bug? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4099226#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...