Queue sharing groups

Queue sharing groups exist only on z/OS® queue managers. A queue sharing group is a group of queue managers that can access the same shared queues. Each member of the queue sharing group has access to the same set of shared queues.

All the queue sharing groups to which the queue managers in IBM MQ Explorer belong are shown in the Queue Sharing Group folder. All the resources that members of a queue sharing group can access are shown in folders in the queue sharing group.

Queue sharing groups have a name of up to four characters. The name must be unique in your network, and must be different from any queue manager names.

We cannot create or configure queue sharing groups in IBM MQ Explorer.

For more information, see Queue sharing groups and clusters in the IBM MQ online product documentation.

Shared queues

A shared queue is a queue that has been defined on a queue manager in a queue sharing group and has the queue sharing group disposition of Shared. A shared queue's object definition is stored in the queue sharing group's shared repository on Db2®, and the messages on the shared queue are stored in a coupling facility structure on a physical coupling facility.

All of the queue managers in the queue sharing group can access the shared queue, which means that they can put and get messages on the shared queue without needing active channels. Because any queue manager can access the shared queue, an application is not dependent on the availability of any one queue manager.

All of the shared queues that belong to a queue manager are shown in the queue manager's folder. All of the shared queues in a queue sharing group are also shown in the queue sharing group's Shared Queues folder.

Group definitions

Group definitions is the collective term for IBM MQ objects that are defined on queue managers in a queue sharing group and have the queue sharing group disposition of Group. Any IBM MQ object that can be defined on a z/OS queue manager can have the queue sharing group disposition of Group. When you create a group definition object, the definition of the object is stored in the shared repository on Db2.

IBM MQ automatically creates a copy of the object (with queue sharing group disposition Copy) for each queue manager and stores it on the queue manager's page set zero with the queue manager's private objects, which have disposition Private. A page set is a data set that is specially formatted for use by IBM MQ. The messages on queues that have disposition Copy are also stored on page sets but they should not be stored on page set zero because if page set zero gets full, IBM MQ cannot function correctly. We can specify which page set the messages are stored on by creating one or more storage class objects which map the queues to page sets.

All of the group definitions that belong to a queue manager are shown in the queue manager's folder. All of the group definitions in a queue sharing group are also shown in the queue-sharing group's Group Definitions folder.