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MQ clusters - Summary of concepts
If you are familiar with WebSphere MQ and distributed queuing, think of a cluster as a network of queue managers maintained by a conscientious systems administrator.
Whenever you create a receiver channel or define a queue, the systems administrator automatically creates corresponding sender channels and remote-queue definitions on the other queue managers.
You do not need to make transmission queue definitions because WebSphere MQ provides a transmission queue on each queue manager. This single transmission queue can be used to carry messages to any other queue manager.
All the queue managers that join a cluster agree to work in this way. They send out information about themselves and about the queues they host, and they receive information about the other members of the cluster.
This information is stored in repositories. Most queue managers retain only the information that they need, that is, information about queues and queue managers with which they need to communicate. Some queue managers retain a full repository of all the information about all queue managers in the cluster.
A cluster-receiver channel is a communication channel similar to a receiver channel. When you define a cluster-receiver channel, not only is the object created on your queue manager, but also information about the channel and the queue manager that owns it is stored in the repositories. The definition of a cluster-receiver channel is a queue manager’s initial introduction to a cluster. Once it has been defined, other queue managers can automatically make corresponding definitions for the cluster-sender end of the channel as needed.
A cluster-sender channel is a communication channel similar to a sender channel. You need a cluster-sender channel only if you want to communicate with another cluster queue manager. When another cluster queue manager wants to communicate with you, your cluster-sender channel is created automatically by reference to the appropriate cluster-receiver channel definition. However, each queue manager must have one manually defined cluster-sender channel, through which it makes its initial contact with the cluster.
Queue managers on platforms that support clusters do not have to be part of a cluster. We can continue to use distributed queuing techniques as well as, or instead of, using clusters.
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