WebSphere Message Brokers
File: ae27040_
Writer: Bill Oppenheimer

Task topic

This build: July 31, 2007 21:28:53

Serialization token - user tasks on z/OS

This topic gives an overview of the steps needed to:
  • Configure a shared input queue for message flows
  • Define a serialization token

Configure a shared input queue for message flows

The WebSphere Message Broker broker makes use of WebSphere MQ queue-sharing groups on z/OS.

Queue managers that can access the same set of shared queues form a group called a queue-sharing group (QSG) and they communicate with each other by means of a coupling facility (CF) that stores the shared queues. A shared queue is a type of local queue whose messages can be accessed by one or more queue managers that are in a QSG.

To further enhance the availability of messages in a QSG, WebSphere MQ detects if another queue manager in the group disconnects from the CF in an unusual way, and completes pending units of work for that queue manager where possible; this is known as peer recovery.

To understand more fully the concepts of shared-queues and queue-sharing groups, see the WebSphere MQ for z/OS Concepts and Planning Guide and perform the following steps:
  • Add a QSG to the DB2 tables
  • Add a queue manager to a QSG
  • Create the shared queue as a member of the QSG

Define a serialization token

Define the same value for the serialization token attribute for each MQInput node that is required to access the shared queue.

For the situations described in the preceding text to work you must:
  • Ensure that the Coupling Facility Structure is at CFLEVEL(3) or above and that you set RECOVER=YES.

    If you do not do this, when an MQInput node attempts to get a message from the shared queue, the action fails with the WebSphere MQ return code 2048(MQRC_PERSISTENT_NOT_ALLOWED)

  • Set the Backout Threshold for the shared queue to at least 2.

    This is to avoid input messages that are in progress being sent to the Dead Letter Queue because, during recovery, a message is restored to the input queue before another broker is able to get it and resume processing.

Related concepts
Overview of message serialization on z/OS
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Copyright IBM Corporation 1999, 2007Copyright IBM Corporation 1999, 2007. All Rights Reserved.
This build: July 31, 2007 21:28:53

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