How to get to the remote queue manager
Overview
You may not always have one channel between each source and target queue manager. Consider these alternative possibilities.
Multi-hopping
If there is no direct communication link between the source queue manager and the target queue manager, it is possible to pass through one or more intermediate queue managers on the way to the target queue manager. This is known as a multi-hop.
You need to define channels between all the queue managers, and transmission queues on the intermediate queue managers.
Sharing channels
As an application designer, you have the choice of forcing your applications to specify the remote queue manager name along with the queue name, or creating a remote queue definition for each remote queue. This definition holds the remote queue manager name, the queue name, and the name of the transmission queue. Either way, all messages from all applications addressing queues at the same remote location have their messages sent through the same transmission queue.
Using different channels
If you have messages of different types to send between two queue managers, you can define more than one channel between the two. There are times when you need alternative channels perhaps for security purposes, or to trade off delivery speed against sheer bulk of message traffic.
To set up a second channel you need to define another channel and another transmission queue, and create a remote queue definition specifying the location and the transmission queue name. Your applications can then use either channel but the messages will still be delivered to the same target queues.
When you use remote queue definitions to specify a transmission queue, your applications must not specify the location (that is, the destination queue manager) themselves. If they do, the queue manager will not make use of the remote queue definitions. Remote queue definitions make the location of queues and the transmission queue transparent to applications. Applications can put messages to a logical queue without knowing where the queue is located and you can alter the physical queue without having to change your applications.
Using clustering
Every queue manager within a cluster defines a cluster-receiver channel. When another queue manager wants to send a message to that queue manager, it defines the corresponding cluster-sender channel automatically. For example, if there is more than one instance of a queue in a cluster, the cluster-sender channel could be defined to any of the queue managers that host the queue. WebSphere MQ uses a workload management algorithm that uses a round-robin routine to select an available queue manager to route a message to.
WebSphere is a trademark of the IBM Corporation in the United States, other countries, or both.
IBM is a trademark of the IBM Corporation in the United States, other countries, or both.