WMQ v7.0.1 and WMB v7 have a new feature for standby processes that make the products more highly available.
The feature in WebSphere MQ, introduced in v7.0.1, is called multi-instance queue managers. The corresponding feature in WebSphere Message Broker, introduced in v7, is called multi-instance brokers. In both cases, the queue manager or broker runs in two processes, one active and the other on standby. If the active one fails, the product automatically fails over to the standby, with virtually no service interruption. Note that any resources the processes use, such as a database, must have their own high availability capabilities.
Multi-instance queue manager
In prior versions, to make WMQ or WMB highly available, one had to use hardware clustering (such as PowerHA (formerly known as HACMP) or Veritas). Hardware clustering may still be the gold standard for HA, but for environments that don't quite need the gold standard, software clustering via multi-instances may be good enough.
This new design reminds me of how the service integration bus in WebSphere Application Server works. An SIB bus is a collection of messaging engines managed by the WAS HA manager. By default, it runs two copies of each messaging engine, an active and a standby. If (parts of) the cluster lose communication with the messaging engine, the HA manager switches them to use the standby. Only one copy of the messaging engine can be active and only that one can maintain a lock on the external storage for the persistent messages. Multi-instance queue managers work in much the same way.
The new Redbook High Availability in WebSphere Messaging Solutions contains a section on multi-instance queue managers and brokers. To quote:
WebSphere MQ V7.0.1 introduced the ability to configure multi-instance queue managers. This capability allows you to configure multiple instances of a queue manager on separate machines, providing a highly available active-standby solution.
WebSphere Message Broker V7 builds on this feature to add the concept of multi-instance brokers. This feature works in the same way by hosting the broker's configuration on network storage and making the brokers highly available.
So if you needed a reason to upgrade to WMQ and WMB 7, now you have it.
Thanks to my colleague Guy Hochstetler who made me aware of this new feature.