Hi Michael
If you leave the JMS receiver channels running while the JMS server is undergoing maintenance, the channels will try to deliver the messages but unable to connect to the server.
The adapter framework will move the messages to status Waiting, and reschedule it for 3 more times of automatic retry every 15 minutes (default setting.) If the 3rd automatic retry still fails, message will be set to System Error. The messages will need to be manually resend once the server is back up.
If the server is going to be down for 2-3 hours, it's best to stop the channels.
Rgds
Eng Swee