Creating and managing queue managers
Before you can use messages and queues, you must create and start at least one queue manager and its associated objects.
Creating a queue manager
A queue manager manages the resources associated with it, in particular the queues that it owns. It provides queuing services to applications for Message Queuing Interface (MQI) calls and commands to create, modify, display, and delete IBM® WebSphere® MQ objects.
To create a queue manager, use the IBM WebSphere MQ control command crtmqm (described in crtmqm). The crtmqm command automatically creates the required default objects and system objects (described in System default objects). Default objects form the basis of any object definitions that you make; system objects are required for queue manager operation. When you have created a queue manager and its objects, use the strmqm command to start the queue manager.
- The installation associated with the queue manager
- The crtmqm command automatically associates a queue manager with the installation from which the crtmqm command was issued. For commands that operate on a queue manager, you must issue the command from the installation associated with the queue manager. You can change the associated installation of a queue manager using the setmqm command. Note the Windows installer does not add the user that performs the install to the mqm group, for more details, see Authority to administer IBM WebSphere MQ on UNIX, Linux® and Windows systems.
- Naming conventions
- Use uppercase names so that you 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, you can name your queue manager
SATURNidentifies a particular queue manager and
QUEUE.MANAGERis an extension you can give to all queue managers. Alternatively, you can omit this, but note that
ACCOUNTS.SATURN.QUEUE.MANAGERare different queue manager names.
If you are using IBM WebSphere MQ for communication with other enterprises, you 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.Note: 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. 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
node should have a default queue manager, though it is possible to configure IBM 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
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.
Creating a default queue manager is described in Creating a default queue manager.
- 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 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. You 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. See Working with queue managers for an example of the MQSC command ALTER.
- 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. See Working with local queues for more information.
- Specify the logging parameters you require
- You 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.
For more information about logging parameters, see Availability, recovery and restart.
For IBM WebSphere MQ for UNIX systems only
You can create
the queue manager directory
/var/mqm/qmgrs/<qmgr>, even on a separate local file system, before you use the crtmqm command. When you use crtmqm, if the
exists, is empty, and is owned by mqm, it is used for the queue manager
data. If the directory is not owned by mqm, the creation fails with
a First Failure Support
Technology ( FFST) message. If the directory is not empty,
a new directory is created.