Before proceeding to the next chapter it is useful to understand the following terminology:
A cluster queue manager can host queues, which it advertises to the other queue managers in the cluster. A cluster queue manager does not have to host or advertise any queues. It can just feed messages into the cluster and receive only responses that are directed explicitly to it, and not to advertised queues.
In WebSphere MQ for z/OS, a cluster queue manager can be a member of a queue-sharing group. In this case, it shares its queue definitions with other queue managers in the same queue-sharing group. For more information about queue-sharing groups see the WebSphere MQ for z/OS Concepts and Planning Guide.
Cluster queue managers are autonomous. They have full control over queues and channels that they define. Their definitions cannot be modified by other queue managers (other than queue managers in the same queue-sharing group).
When you make or alter a definition on a cluster queue manager, the information is sent to the full repository queue manager and the repositories in the cluster are updated accordingly.
A cluster queue can be a queue that is shared by members of a queue-sharing group in WebSphere MQ for z/OS.
The other queue managers in the cluster inquire about the information in the full repositories and build up their own subsets of this information in partial repositories. A queue manager's partial repository contains information about only those queue managers with which the queue manager needs to exchange messages. The queue managers request updates to the information they need, so that if it changes, the full repository queue manager will send them the new information. For much of the time a queue manager's partial repository has all the information it needs to perform within the cluster. When a queue manager needs some additional information, it makes inquiries of the full repository and updates its partial repository. The queue managers use a queue called SYSTEM.CLUSTER.COMMAND.QUEUE to request and receive updates to the repositories. This queue is one of the default objects, except on WebSphere MQ for z/OS where it is defined as part of queue manager customization.
The full repository queue managers themselves have cluster-sender channels that point to each other. They use them to communicate cluster status changes to each other.
It is of little importance which full repository a queue manager's CLUSSDR channel definition points to. Once the initial contact has been made, further cluster queue manager objects are defined automatically as necessary so that the queue manager can send cluster information to every full repository, and messages to every queue manager.
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