The procedure that you must follow to migrate a WebSphere MQ broker that is part of a multi-broker network is basically the same as that needed to migrate a single broker.
Before you start the migration, you must consider:
Refer to Planning for migration for more information.
The following sequence of figures illustrates the migration of a network of three brokers. The actions taken to migrate the network assumes that the three brokers are migrated one at a time, and that all three are to be grouped in a single collective in the WebSphere Message Broker broker domain.
The migration is completed in a number of separate steps. Each step is best taken when network traffic is low (for example, at weekends). The whole migration is planned in three stages:
The steps that you need to take to migrating a single broker within a network are exactly the same as those that you need to take to migrate a standalone WebSphere MQ broker. See Migrating WebSphere MQ brokers.
The connection between the LONDON and NEWYORK brokers is a WebSphere MQ connection. The workbench only recognizes WebSphere Message Broker brokers, and therefore only LONDON has been defined to it. A WebSphere Message Broker connection cannot be created at this stage.
This mixed network is in a perfectly valid state. It can remain in this state until you are ready to do the next stage of the migration.
Follow the step-by-step procedure for migrating a single broker for broker NEWYORK. This is described in Migrating WebSphere MQ brokers.
The LONDON and NEWYORK brokers are still connected by a WebSphere MQ connection. They can remain connected in this way for as long as necessary. However, to develop applications that use the functions provided by WebSphere Message Broker you must join the two WebSphere Message Broker brokers together using the workbench.
The connection can be upgraded to a WebSphere Message Broker connection by first removing the original WebSphere MQ connection between LONDON and NEWYORK.
mqsiclearmqpubsub NEWYORK -n LONDON mqsiclearmqpubsub LONDON -n NEWYORK
Now use the workbench to define the relationship between the two brokers, LONDON and NEWYORK. Both brokers are already defined, but the collective to which they are to be assigned is not. You can define this collective from the Topology view, and assign the two brokers to it. All brokers in a collective are assumed to be connected, so you do not have to make those connections using the workbench.
The two brokers, LONDON and NEWYORK, are no longer in a parent-child relationship but are neighbors within a collective. The topology of the WebSphere Message Broker network is not based on a hierarchical structure as was the WebSphere MQ network.
Now that LONDON and NEWYORK form a collective, there is no root node left in the WebSphere MQ network. NEWYORK is the gateway between the WebSphere MQ broker (TOKYO) and the WebSphere Message Broker collective of brokers.
The final WebSphere MQ broker, TOKYO, is now ready to be migrated. Follow the procedure described in Migrating WebSphere MQ brokers.
mqsiclearmqpubsub NEWYORK -n TOKYO mqsiclearmqpubsub TOKYO -n NEWYORK
Now use the workbench to add the TOKYO broker to the WebSphere Message Broker network, and to the collective. The operation of a collective requires that all brokers have direct physical connections with each other (via WebSphere MQ).
Before the topology of the new WebSphere Message Broker network can be deployed, a WebSphere MQ connection between LONDON and TOKYO is required. A series of WebSphere MQ commands must be invoked to define the channels and transmission queues that support two-way traffic.
When you have completed the migration of all the brokers in the collective, you have removed the single point of failure at the NEWYORK broker. Subscribers on the LONDON broker can receive publications from the TOKYO broker even when the NEWYORK broker is not running.
Before migration, traffic between brokers was always routed through NEWYORK, the root node, which was therefore the single point of failure.
For further details of connecting brokers to each other, see Configuring WebSphere Message Broker. For more general information about distributed WebSphere MQ networks, refer to WebSphere MQ Intercommunication.