Diagnosing problems in the Queue Control Facility Message Requeuer

The Queue Control Facility Message Requeuer (MRQ) processor module (DFSQMRQ0), which is part of the IMS™ Transaction Manager, provides diagnostic information for diagnosing errors while running the IBM® IMS Queue Control Facility for z/OS® (QCF).

Although problems can be diagnosed separately in the QCF product by using SCRAPLOG records and in the Queue Control Facility processor module by using 6701-MRQE diagnostic records, QCF and the Queue Control Facility processor work together to allow inserting and loading, querying, recovering, deleting and unloading, recovering, and viewing messages on the IMS message queue data sets and shared message queue structures.

In this topic, the information about SCRAPLOG records also applies to SCRAPSEL and SCRAPCAN records. The SCRAPSEL, SCRAPCAN, and SCRAPLOG data sets are generated by the IQCSELCT, IQCCANCL, and IQCINSRT modules of QCF, respectively, and are identical in both format and function.

• QCF functions help you accomplish the following tasks:
  • Message queue recovery when you want to return messages to the IMS queue for reprocessing.
  • Application recovery when you want to return messages to the IMS queue for reprocessing.
  • IMS queue maintenance (you can query, browse, unload, and load IMS nonshared queue environments).
  • Message queue migration and fallback.
  • Stress, regression, and application testing when transaction data is needed to simulate production loads or application input.
• A queue overflow protection function monitors queue usage and takes action to prevent queue utilization from reaching critical thresholds (non-shared queues environment).
• An ISPF front-end enables you to select QCF functions and selection criteria to complete the following tasks:
  • Query messages (or IMS status) on the queue
  • Unload (delete) messages from the queue
  • Load messages onto the IMS message queues
  • Release or terminate waiting tasks (nonshared queue environment)
  • Maintain the tables associated with queue overflow protection (nonshared queue environment)