The dead letter queue is a TAC queue with the fixed name KDCDLETQ. It is always available to save queued messages sent to transaction codes, TAC queues, LPAPs or OSI-LPAPs but which could not be processed. During generation, the saving of queued messages in the dead letter queue can be activated or deactivated for each message destination individually using the TAC, LPAP or OSI-LPAP statement's DEAD-LETTER-Q parameter.
To be able to process the messages in the dead letter queue, for example after eliminating an error, you must either reassign them to their original destination or assign them to an new destination. You can use DADM MV to move an individual message and DADM MA to move all the messages in the dead letter queue to a specified or to the original queues. Please note that messages can only be moved to a destination of the same type as the original destination (TAC → TAC, LPAP → LPAP, OSI-LPAP → OSI-LPAP).
The K134 message makes it possible to monitor the message volume arriving in the dead letter queue (see openUTM manual “Generating Applications”, DEAD-LETTER-Q-ALARM operand in the MAX statement).
Preventing a page pool bottleneck
Since the dead letter queue is stored in the page pool, the page pool should be generated with enough space to save messages in the dead letter queue.
The following actions are available to prevent or remove a bottleneck in the page pool:
Moving messages from the dead letter queue (DADM MV/MA).
Deleting messages from the dead letter queue (DADM DL/DA).
Generating QLEV to limit the maximum number of messages in the dead letter queue.
Temporarily locking the dead letter queue (STATUS = OFF).
Temporarily deactivating the saving of messages in the dead letter queue for individual destinations, e.g. using WinAdmin, WebAdmin or programmed administration.