Using clusters for workload management

By defining multiple instances of a queue on different queue managers in a cluster you can spread the work of servicing the queue over multiple servers. There are several factors that can prevent messages being requeued to a different queue manager in the event of failure.

As well as setting up clusters to reduce system administration, you can create clusters in which more than one queue manager hosts an instance of the same queue.

You can organize your cluster such that the queue managers in it are clones of each other. Each queue manager is able to run the same applications and have local definitions of the same queues. [z/OS]For example, in a z/OS® parallel sysplex the cloned applications might access data in a shared Db2® or Virtual Storage Access Method (VSAM) database. You can spread the workload between your queue managers by having several instances of an application. Each instance of the application receives messages and runs independently of the others.

The advantages of using clusters in this way are as follows:
  • Increased availability of your queues and applications.
  • Faster throughput of messages.
  • More even distribution of workload in your network.

Any one of the queue managers that hosts an instance of a particular queue can handle messages destined for that queue, and applications do not name a queue manager when sending messages. If a cluster contains more than one instance of the same queue, IBM® MQ selects a queue manager to route a message to. Suitable destinations are chosen based on the availability of the queue manager and queue, and on a number of cluster workload-specific attributes associated with queue managers, queues, and channels. See Workload balancing in clusters.

[z/OS]In IBM MQ for z/OS, queue managers that are in queue-sharing groups can host cluster queues as shared queues. Shared cluster queues are available to all queue managers in the same queue-sharing group. For example, in A cluster with multiple instances of the same queue, either or both of the queue managers QM2 and QM4 can be a shared-queue manager. Each has a definition for the queue Q3. Any of the queue managers in the same queue-sharing group as QM4 can read a message put to the shared queue Q3. Each queue-sharing group can contain up to 32 queue managers, each with access to the same data. Queue sharing significantly increases the throughput of your messages.

See the following subtopics for more information about cluster configurations for workload management: