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Guidelines for creating queue managers

 

 

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Naming conventions

Use uppercase names so that we can communicate with queue managers on all platforms. Remember that names are assigned exactly as you enter them. To avoid the inconvenience of lots of typing, do not use unnecessarily long names.

Specify a unique queue manager name

When you create a queue manager, ensure that no other queue manager has the same name anywhere in your network. Queue manager names are not checked when the queue manager is created, and names that are not unique prevent you from creating channels for distributed queuing.

One way of ensuring uniqueness is to prefix each queue manager name with its own unique node name. For example, if a node is called ACCOUNTS, we can name your queue manager...

ACCOUNTS.SATURN.QUEUE.MANAGER

...where SATURN identifies a particular queue manager and QUEUE.MANAGER is an extension we can give to all queue managers. Alternatively, we can omit this, but note that...

ACCOUNTS.SATURN

...and...

ACCOUNTS.SATURN.QUEUE.MANAGER

...are different queue manager names.

If you are using WebSphere MQ for communication with other enterprises, we can also include your own enterprise name as a prefix. This is not done in the examples, because it makes them more difficult to follow.

Queue manager names in control commands are case-sensitive. This means that you are allowed to create two queue managers with the names...

jupiter.queue.manager

...and...

JUPITER.queue.manager

However, it is better to avoid such complications.

Limit the number of queue managers

You can create as many queue managers as resources allow. However, because each queue manager requires its own resources, it is generally better to have one queue manager with 100 queues on a node than to have ten queue managers with ten queues each.

In production systems, many processors can be exploited with a single queue manager, but larger server machines might run more effectively with multiple queue managers.

Specify a default queue manager

Each node should have a default queue manager, though it is possible to configure WebSphere MQ on a node without one. The default queue manager is the queue manager that applications connect to if they do not specify a queue manager name in an MQCONN call. It is also the queue manager that processes MQSC commands when you invoke the runmqsc command without specifying a queue manager name.

Specifying a queue manager as the default replaces any existing default queue manager specification for the node.

Changing the default queue manage can affect other users or applications. The change has no effect on currently-connected applications, because they can use the handle from their original connect call in any further MQI calls. This handle ensures that the calls are directed to the same queue manager. Any applications connecting after you have changed the default queue manager connect to the new default queue manager. This might be what you intend, but you should take this into account before you change the default.

Specify a dead-letter queue

The dead-letter queue is a local queue where messages are put if they cannot be routed to their intended destination.

It is important to have a dead-letter queue on each queue manager in your network. If you do not define one, errors in application programs might cause channels to be closed, and replies to administration commands might not be received.

For example, if an application tries to put a message on a queue on another queue manager, but gives the wrong queue name, the channel is stopped and the message remains on the transmission queue. Other applications cannot then use this channel for their messages.

The channels are not affected if the queue managers have dead-letter queues. The undelivered message is simply put on the dead-letter queue at the receiving end, leaving the channel and its transmission queue available.

When you create a queue manager, use the -u flag to specify the name of the dead-letter queue. We can also use an MQSC command to alter the attributes of a queue manager that you have already defined to specify the dead-letter queue to be used.

Specify a default transmission queue

A transmission queue is a local queue on which messages in transit to a remote queue manager are queued before transmission. The default transmission queue is the queue that is used when no transmission queue is explicitly defined. Each queue manager can be assigned a default transmission queue.

When you create a queue manager, use the -d flag to specify the name of the default transmission queue. This does not actually create the queue; you have to do this explicitly later on.

Specify the logging parameters you require

We can specify logging parameters on the crtmqm command, including the type of logging, and the path and size of the log files.

In a development environment, the default logging parameters should be adequate. However, you can change the defaults if, for example:

• You have a low-end system configuration that cannot support large logs.

• You anticipate a large number of long messages being on your queues at the same time.

• You anticipate a lot of persistent messages passing through the queue manager.

Once you have set the logging parameters, some of them can only be changed by deleting the queue manager and recreating it with the same name but with different logging parameters.

For more information about logging parameters, see Recovery and restart.

Installing multiple queue managers

If you install multiple queue managers with different logical volumes for each queue manager, the ftok function might cause shared memory problems. The ftok function calculates the shared memory key from the node and the minor number of the housing logical volume. On AIX, shared memory problems can occur if two queue managers are installed in an HACMP™ environment with different logical volumes that have identical minor device numbers.

These shared memory problems do not occur if the different logical volumes are created such that they have different minor device numbers.

 

Parent topic:

Creating a queue manager

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