- All AQ Queues have a default associated exception queue where messages that "may not be consumed within given constraints" are moved.
- By default the exception queue name is called AQ$_[ORIGINAL_QUEUE_NAME]_E. For example, if the original normal queue is called MYQUEUE, its default exception queue is called AQ$_MYQUEUE_E. I notice that for example, in SQL Developer, I can't see the exception queue in the "Queues" tree (but it "exists"). Also by default, the default exception queues are not enabled for dequeuing. Yoy can use this instruction to enable dequeuing: dbms_aqadm.start_queue(queue_name=>'MYQUEUE', enqueue=>FALSE,dequeue=>TRUE). You can't enable an exception queue for enqueuing. Here is additional information about the exception queues.
- By default, both queues (the normal queue and the exception queue), are supported by the same queue table. You can check it by directly querying the queue table (MYQUEUETABLE) and looking the Q_NAME column or by querying the queue table AQ view (AQ$MYQUEUETABLE) and looking the QUEUE column (this is the prefered way). The value for the "expired" messages is AQ$_MYQUEUE_E and the value for the normal messages is MYQUEUE.
- You can use an "user-defined exception queue", but it is set through a message header; that is, at message level and not at queue level. At the message enqueue time, you can set the exception queue for that message through a header (JMS_OracleExcpQ); if that message expires, it will be moved to that user-defined exception queue. Here, you can check some good instructions to use it in PL/SQL or Java JMS.
Here are some references in My Oracle Support:
