Designing Dialogs › Design Considerations › Working Storage Areas › Queue Records

Queue Records

Queue records can be used as work records that are shared by tasks on all DC/UCF system terminals. Entries are directed to a queue with database commands embedded in the dialogs or batch programs. Queues can transfer data across the entire DC/UCF system and are maintained across system shutdowns and crashes. Currencies and locks are not passed between tasks.

Note: When used in a sysplex environment, the queue area may be shared between multiple DC/UCF systems. For more information on shared queues, please see the CA IDMS System Operations Guide manual.

Queue records have the following characteristics:

• A queue header record is allocated either at system generation or by an application dialog.
• Queue records participate in a set in the dictionary; this set is commonly referred to as a queue.
• Queue records are locked by each task; no other task can use them until the locks are released.

Queues created at system generation with the system QUEUE statement can be accessed by an CA ADS application. Additionally, an application can create its own queues by requesting storage space with a GET QUEUE statement in the dialog process code.

An application can use queue records to accomplish the following functions:

• Automatically initiate a task — The DC/UCF system initiates a task that processes the queue entries when the number of entries in a queue reaches a specified limit or when a specified time interval has passed. For example, an application can write records to a queue and the system will route the records to a printer when the collected records exceed the specified limit.
• Avoid prime time updating — Records that need to be updated can be collected on a queue; the queue can be accessed by a batch program at a low-use time.
• Prevent run-away tasks — A maximum limit can be established for the number of entries permitted in a queue. The UPPER LIMIT parameter of the QUEUE statement is especially useful in a test environment to prevent a looping program from filling the scratch/queue area.