The dead-letter queue handler utility (CSQUDLQH)

 

A dead-letter queue (DLQ) is a holding queue for messages that cannot be delivered to their destination queues. Every queue manager in a network should have an associated DLQ.

Queue managers, message channel agents, and applications can put messages on the DLQ. All messages on the DLQ should be prefixed with a dead-letter header structure, MQDLH. Messages put on the DLQ by a queue manager or by a message channel agent always have a dead-letter header; ensure that applications putting messages on the DLQ supply a dead-letter header as well. The Reason field of the MQDLH structure contains a reason code that identifies why the message is on the DLQ.

There should be a routine that runs regularly to process messages on the DLQ. WebSphere MQ supplies a default dead-letter queue handler (DLQ handler) called CSQUDLQH. A user-written rules table supplies instructions to the DLQ handler, for processing messages on the DLQ. That is, the DLQ handler matches messages on the DLQ against entries in the rules table. When a DLQ message matches an entry in the rules table, the DLQ handler performs the action associated with that entry.