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What is DeadLetter Queue? - Middleware News

DLQ
If a message arrives at a queue manager but there is no queue there to receive it, the message is put on the dead-letter queue as usual. If there is no dead-letter queue, the channel fails and retries, as described in the MQ Intercommunication book.

Again : For example, if an application tries to put a message on a queue on another queue manager, but gives the wrong queue name, the channel is stopped and the message remains on the transmission queue. Other applications cannot then use this channel for their messages.

Again : If you do not, and the MCA is unable to put a message, it is left on the transmission queue and the channel is stopped.

Again : If all the retries are unsuccessful, the message is written to the dead-letter queue. If there is no dead-letter queue available, the channel stops.

You can create it by using the DEADQ attribute on the ALTER QMGR command to specify one later.
DLQ monitor : MS71 !
How to WRITE into it
Define a cluster of 3 queue managers : TQM1, TQM2 and TQM3.
TQM1 and TQM2 share the queue WLMQ1 on the cluster. This is, TQM3 sees two "cluster" queues.
On TQM3, define an ALIAS for WLMQ1, named WLMAQ.
If an application writes - connecting to TQM3 - into WLMAQ, then the messages are split between WLMQ1 on both TQM1 and TQM2.
Now, define a queue manager external to the cluster, named TQM4.
Define a REMOTE QUEUE on it, called RMQ99, pointing to WLMAQ on TQM3. And a CHANNEL also ... and activate it !
If an application sends a message connecting to TQM4 and using this Remote Queue RMQ99, it is placed in the TQM3's Dead Letter Queue (named TQM3DLQ) with Reason Code
d'2082 = MQRC_UNKNOWN_ALIAS_BASE_Q - see.
See "Dead-Letter Header" !
How to WRITE into it (2) :
put a message into a XMIT queue, and get RC = d'0271 = MQFB_XMIT_Q_MSG_ERROR Feedback indicating that a message channel agent has found that a message on the transmission queue is not in the correct format. The message channel agent puts the message on the dead-letter queue using this feedback code.
Requires "Running" channel !
How to READ from it
  • DLQ handler {easy !}
  • RFHutil
    RFHUtil + Read Queue + "DLQ" + uncheck "Include DLQH" on last Tab + Write Queue + "Q1" + and msg is on Q1, without DLQH
  • MA0T ?
  • If you want to move one single message: MQMON (SupportPac MO71)

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