Queue managers

A queue manager supplies an application with WebSphere MQ services. A program must have a connection to a queue manager before it can use the services of that queue manager. A program can make this connection explicitly (using the MQCONN or MQCONNX call), or the connection might be made implicitly (this depends on the platform and the environment in which the program is running).

Queues belong to queue managers, but programs can send messages to queues that belong to any queue manager.

Attributes of queue managers

Associated with each queue manager is a set of attributes (or properties) that define its characteristics. Some of the attributes of a queue manager are fixed when it is created; you can change others using the WebSphere MQ commands. You can inquire about the values of all the attributes, except those used for Secure Sockets Layer (SSL) encryption, using the MQINQ call.

The fixed attributes include:

• The name of the queue manager
• The platform on which the queue manager runs (for example, z/OS)
• The level of system control commands that the queue manager supports
• The maximum priority that you can assign to messages processed by the queue manager
• The name of the queue to which programs can send WebSphere MQ commands
• The maximum length of messages the queue manager can process (Fixed only in WebSphere MQ for z/OS)
• Whether the queue manager supports syncpointing when programs put and get messages

The changeable attributes include:

• A text description of the queue manager
• The identifier of the character set the queue manager uses for character strings when it processes MQI calls
• The time interval that the queue manager uses to restrict the number of trigger messages
• The time interval that the queue manager uses to determine how often queues are to be scanned for expired messages (WebSphere MQ for z/OS only)
• The name of the queue manager's dead-letter (undelivered message) queue
• The name of the queue manager's default transmission queue
• The maximum number of open handles for any one connection
• The enabling and disabling of various categories of event reporting
• The maximum number of uncommitted messages within a unit of work

For a full description of all the attributes, see WebSphere MQ Application Programming Reference.

Queue managers and workload management

You can set up a cluster of queue managers that has more than one definition for the same queue (for example, the queue managers in the cluster could be clones of each other). Messages for a particular queue can be handled by any queue manager which hosts an instance of the queue. A workload-management algorithm decides which queue manager handles the message and so spreads the workload between your queue managers. See WebSphere MQ Queue Manager Clusters for further information.