Designing Dialogs › Design Considerations › Queue Records

Queue Records

Queue records can be used as work records that are shared by tasks on all DC/UCF 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.

Characteristics

Queue records have the following characteristics:

• A queue header record is allocated either at system compilation or by an application dialog.
• Queue records participate in a set in the data 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 compilation with the system QUEUE statement can be accessed by a 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.

Functions

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

• Automatically initiate a task — DC/UCF 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.

For detailed descriptions of the queue management commands, refer to the CA ADS Reference Guide.