What is queue name resolution?

Queue name resolution is vital to DQM. It removes the need for applications to be concerned with the physical location of queues, and insulates them against the details of networks.

A systems administrator can move queues from one queue manager to another, and change the routing between queue managers without applications needing to know anything about it.

In order to uncouple from the application design the exact path over which the data travels, it is necessary to introduce a level of indirection between the name used by the application when it refers to the target queue, and the naming of the channel over which the flow occurs. This indirection is achieved using the queue name resolution mechanism.

In essence, when an application refers to a queue name, the name is mapped by the resolution mechanism either to a transmission queue or to a local queue that is not a transmission queue. For mapping to a transmission queue, a second name resolution is needed at the destination, and the received message is placed on the target queue as intended by the application designer. The application remains unaware of the transmission queue and channel used for moving the message.

Note: The definition of the queue and channel is a system management responsibility and can be changed by an operator or a system management utility, without the need to change applications.

An important requirement for the system management of message flows is that alternative paths need to be provided between queue managers. For example, business requirements might dictate that different classes of service are sent over different channels to the same destination. This decision is a system management decision and the queue name resolution mechanism provides a flexible way to achieve it. The Application Programming Guide describes this in detail, but the basic idea is to use queue name resolution at the sending queue manager to map the queue name supplied by the application to the appropriate transmission queue for the type of traffic involved. Similarly at the receiving end, queue name resolution maps the name in the message descriptor to a local (not a transmission) queue or again to an appropriate transmission queue.

Not only is it possible for the forward path from one queue manager to another to be partitioned into different types of traffic, but the return message that is sent to the reply-to queue definition in the outbound message can also use the same traffic partitioning. Queue name resolution satisfies this requirement and the application designer need not be involved in these traffic partitioning decisions.

The point that the mapping is carried out at both the sending and receiving queue managers is an important aspect of the way name resolution works. This mapping allows the queue name supplied by the putting application to be mapped to a local queue or a transmission queue at the sending queue manager, and again remapped to a local queue or a transmission queue at the receiving queue manager.

Reply messages from receiving applications or MCAs have the name resolution carried out in the same way, allowing return routing over specific paths with queue definitions at all the queue managers on route.