Overview of the Common Queue Server

The Common Queue Server (CQS) is an internal interface by which IMS communicates with shared message queues. You can use IMS commands to initiate CQS requests.

The CQS address space is started by the IMS.

CQS provides the following services:
  • Notifies registered clients when work exists on the shared queues.
  • Provides clients with an interface for accessing shared queues and CQS.
  • Writes CQS system checkpoint information to a CQS checkpoint data set.
  • Writes structure checkpoint information to an SRDS for recovery of a shared-queues list structure.
  • Provides structure recovery and overflow processing for the shared-queues list structure.
  • Drives the following CQS client exit routines:
    • The Client CQS Event exit routine notifies the client of system events, such as CQS abnormal termination and CQS restart completion.
    • The Client Structure Event exit routine notifies the client of structure events, such as structure copy, structure recovery, structure overflow, structure checkpoint, and structure resynchronization.
    • The Client Structure Inform exit routine notifies the client when work exists on the shared queues.
  • Drives the following CQS user-supplied exit routines:
    • The CQS Queue Overflow user-supplied exit routine allows the exit to approve or reject a queue that CQS selects for overflow.
    • The CQS Initialization/Termination user-supplied exit routine is notified when CQS initializes and when CQS terminates after disconnecting from all structures (under normal termination conditions).
    • The CQS Client Connection user-supplied exit routine participates in connecting clients to structures and in disconnecting clients from structures.
    • The CQS Structure Statistics user-supplied exit routine gathers structure statistics during CQS system checkpoints.
    • The CQS Structure Event user-supplied exit routine tracks structure activity, such as structure checkpoint, structure rebuild, structure overflow, and structure status change. It also tracks when CQS connects to a structure or disconnects from a structure.
  • Provides the Log Print utility with sample JCL. By using the sample JCL, you can print log records from the z/OS® log.