UNLOAD function description

The UNLOAD function unloads (or deletes) messages from the IMS message queues, or removes messages for requeuing, according to your specifications.

You can use the UNLOAD function to perform the following tasks:

  • To clean up the queues by removing unnecessary messages
  • To remove messages for requeuing
  • To perform stress testing

When you use the UNLOAD function as a migration or fallback aid, the unload data set is used to requeue messages across supported IMS releases. Messages that are created on one supported release of IMS can be inserted into another supported release of IMS if the involved source and destination resources, such as LTERMs, transactions, MSC names, and other destination resources are defined on both systems.

UNLOAD produces reports on the messages that its logic unloads. You can specify an age limit that these messages must meet in order to be included in the unload reports.

UNLOAD logic selects records from the message queues for possible later insertion by the load function logic or for purely informational purposes. UNLOAD logic performs the following tasks:

  1. Processes control blocks that were built by IMS Queue Control Facility control processing logic from input control statements to make the following determinations:
    • Determines queue selection from the QUEUETYPE= keyword of the FUNCTION statement
    • Determines record selection criteria for date and timestamps, and record type from the SELECT statement
    • Determines record selection criteria for message sources and destinations from the INCLUDE and EXCLUDE statements
  2. Discards records that fail to meet the selection criteria of the SELECT, INCLUDE, and EXCLUDE statements
  3. Writes records that do meet the selection criteria of the FUNCTION, SELECT, and INCLUDE statements to the unload data set
  4. Produces reports about the number and types of records that UNLOAD unloaded from the message queues
  5. Returns control to IMS Queue Control Facility control processing logic

The job steps that are required for the UNLOAD function are as follows: UNLOAD