TD Queue Definitions

TD queue definitions describe transient data queues - CICS-managed sequential queues used for passing data between tasks, feeding printers, and triggering work automatically.

The three types of TD queue

• EXTRA - the queue lives outside CICS, usually a sequential data set or a printer. CICS reads from or writes to it like a file.
• INTRA - the queue lives inside CICS. Tasks write records with EXEC CICS WRITEQ TD and other tasks read them back.
• INDIRECT - an alias name that points at another EXTRA or INTRA queue, so programs can use a stable name while the real queue moves.
• Intrapartition queues can trigger ATI - automatic transaction initiation - when the queue depth hits a trigger level.

Key attributes of a TDQUEUE definition

• QUEUE - the 1 to 4 character queue name used in EXEC CICS WRITEQ TD / READQ TD.
• TYPE - EXTRA, INTRA or INDIRECT.
• DDNAME - for EXTRA queues, the DD name of the data set in the CICS JCL.
• TRIGLEVEL - for INTRA queues, the number of records that starts ATI.
• ATITRANID - the transaction started automatically when TRIGLEVEL is reached.
• ATITERMID / ATIFACILITY - where the triggered transaction runs.
• ATITIME and ATIUSERID - when it may run and under which user id.
• RECOVSTATUS - PHYSICAL or LOGICAL recovery of queue records after a failure.
• FACILITYID - for INDIRECT queues, the real queue this name points to.

Automatic transaction initiation (ATI)

• Set TRIGLEVEL(n) and ATITRANID on an INTRA queue definition.
• Each WRITEQ TD adds a record. When the count reaches n, CICS starts the ATI transaction automatically.
• The triggered transaction reads the records with READQ TD and processes them - a classic print or batch-feed pattern.
• ATI only fires for INTRA queues with a trigger level defined; EXTRA queues never trigger.

Example - define an INTRA queue that triggers a print transaction every 50 records: