First thing is I did it on JBoss4.0.3 with Webspherev6.0! But one thing I couldn't understand. Whenever I send a message manually to a queue, the "Openning input count" property of the queue would increase by 1 accordingly(after the message was consumed by MDB). And when it reached 16, it stop increasing and maintain at 16. I wonder what the property"Openning input count" stand for and why the "Openning input count" property stops at 16(a conn pool or something?).