This is the JBoss Messaging forum, please use the appropriate forum.
Andy, I think what chiatra is asking is if the cache data provided by JBossMQ is also being provided by JBoss Messaging and if so in which MBean, and if not, if there are any plans to provide such information.
JBM 1.4 is a new architecture. There is no equivalent MBean for Message Cache.
The PostOffice will route messages directly to the Queues, and depending on the number of messages and configuration messages are stored on the Database, what is called Paging.
On JBossMQ this is completely different, as it is based on the % Memory consumption.
I suggest you reading the documentation about JBoss Messaging 1.4+.