Work with remote queues

A remote queue is a local definition of a remote queue. That is, a definition on a local queue manager that refers to a queue on a remote queue manager.

You do not have to define a remote queue from a local position, but the advantage of doing so is that applications can refer to the remote queue by its locally-defined name instead of having to specify a name that is qualified by the ID of the queue manager on which the remote queue is located.

How local definitions of remote queues work

An application connects to a local queue manager and then issues an MQOPEN call. In the open call, the queue name specified is that of a remote queue definition on the local queue manager. The remote queue definition supplies the names of the target queue, the target queue manager, and optionally, a transmission queue. To put a message on the remote queue, the application issues an MQPUT call, specifying the handle returned from the MQOPEN call. The queue manager uses the remote queue name and the remote queue manager name in a transmission header at the start of the message. This information is used to route the message to its correct destination in the network.

As administrator, we can control the destination of the message by altering the remote queue definition.

The following example shows how an application puts a message on a queue owned by a remote queue manager. The application connects to a queue manager, for example, saturn.queue.manager. The target queue is owned by another queue manager.

On the MQOPEN call, the application specifies these fields:

Field value	Description
ObjectName CYAN.REMOTE.QUEUE	Specifies the local name of the remote queue object. This defines the target queue and the target queue manager.
ObjectType (Queue)	Identifies this object as a queue.
ObjectQmgrName Blank or saturn.queue.manager	This field is optional. If blank, the name of the local queue manager is assumed. (This is the queue manager on which the remote queue definition exists.)

After this, the application issues an MQPUT call to put a message onto this queue.

On the local queue manager, we can create a local definition of a remote queue using the following MQSC commands:

DEFINE QREMOTE (CYAN.REMOTE.QUEUE) +
DESCR ('Queue for auto insurance requests from the branches') +
RNAME (AUTOMOBILE.INSURANCE.QUOTE.QUEUE) +
RQMNAME (jupiter.queue.manager) +
XMITQ (INQUOTE.XMIT.QUEUE)

where:

QREMOTE (CYAN.REMOTE.QUEUE)

Specifies the local name of the remote queue object. This is the name that applications connected to this queue manager must specify in the MQOPEN call to open the queue AUTOMOBILE.INSURANCE.QUOTE.QUEUE on the remote queue manager jupiter.queue.manager.

DESCR ('Queue for auto insurance requests from the branches')

Provides additional text that describes the use of the queue.

RNAME (AUTOMOBILE.INSURANCE.QUOTE.QUEUE)

Specifies the name of the target queue on the remote queue manager. This is the real target queue for messages sent by applications that specify the queue name CYAN.REMOTE.QUEUE. The queue AUTOMOBILE.INSURANCE.QUOTE.QUEUE must be defined as a local queue on the remote queue manager.

RQMNAME (jupiter.queue.manager)

Specifies the name of the remote queue manager that owns the target queue AUTOMOBILE.INSURANCE.QUOTE.QUEUE.

XMITQ (INQUOTE.XMIT.QUEUE)

Specifies the name of the transmission queue. This is optional; if the name of a transmission queue is not specified, a queue with the same name as the remote queue manager is used.

In either case, the appropriate transmission queue must be defined as a local queue with a Usage attribute specifying that it is a transmission queue (USAGE(XMITQ) in MQSC commands).

An alternative way of putting messages on a remote queue

Use a local definition of a remote queue is not the only way of putting messages on a remote queue. Applications can specify the full queue name, including the remote queue manager name, as part of the MQOPEN call. In this case, we do not need a local definition of a remote queue. However, this means that applications must either know, or have access to, the name of the remote queue manager at run time.

Use other commands with remote queues

We can use MQSC commands to display or alter the attributes of a remote queue object, or we can delete the remote queue object. For example:

• To display the remote queue's attributes:

  DISPLAY QUEUE (CYAN.REMOTE.QUEUE)
  

• To change the remote queue to enable puts. This does not affect the target queue, only applications that specify this remote queue:

  ALTER QREMOTE (CYAN.REMOTE.QUEUE) PUT(ENABLED)
  

• To delete this remote queue. This does not affect the target queue, only its local definition:

  DELETE QREMOTE (CYAN.REMOTE.QUEUE)
  

Note: When you delete a remote queue, you delete only the local representation of the remote queue. You do not delete the remote queue itself or any messages on it.

• Use remote queue definitions as aliases
  In addition to locating a queue on another queue manager, we can also use a local definition of a remote queue for queue manager aliases and reply-to queue aliases. Both types of alias are resolved through the local definition of a remote queue. We must set up the appropriate channels for the message to arrive at its destination.

Parent topic: Work with local IBM MQ objects