IBM MQ objects

Queue managers define the properties of IBM® MQ objects. The values of these properties affect the way in which IBM MQ processes these objects. You create and manage objects using IBM MQ commands and interfaces. From your applications, you use the Message Queue Interface (MQI) to control objects. Objects are identified by an IBM MQ object descriptor (MQOD) when addressed from a program.

Object administration

The administration of objects includes the following tasks:
  • Starting and stopping queue managers.
  • Creating objects, particularly queues, for applications.
  • Displaying or altering the attributes of objects.
  • Deleting objects.
  • Working with channels to create communication paths to queue managers on other (remote) systems.
  • Creating clusters of queue managers to simplify the overall administration process, and to balance workload.

With the exception of dynamic queues, objects must be defined to the queue manager before you can work with them.

When you use an IBM MQ command to carry out an object administration operation, the queue manager checks that you have the required level of authority to perform the operation. Similarly, when an application uses the MQOPEN call to open an object, the queue manager checks that the application has the required level of authority before it allows access to that object. The checks are made on the name of the object being opened.

You can define and manage objects by using the following methods:
You can also manage objects by using the following methods:

[AIX, Linux, Windows]For sequences of IBM MQ commands on AIX®, Linux, and Windows, you can use the MQSC facility to run a series of commands held in a file. For more information, see Administering IBM MQ using MQSC commands.

[IBM i]For sequences of IBM MQ for IBM i commands that you use regularly you can write CL programs. For more information, see Managing IBM MQ for IBM i using CL commands.

[z/OS]For sequences of IBM MQ for z/OS commands that you use regularly, you can write administration programs that create messages containing commands and that put these messages on the system-command input queue. The queue manager processes the messages on this queue in the same way that it processes commands entered from the command line or from the operations and control panels. This technique is described in the Writing programs to administer IBM MQ, and demonstrated in the Mail Manager sample application delivered with IBM MQ for z/OS. For a description of this sample, see Sample programs for IBM MQ for z/OS .

Object attributes

The properties of an object are defined by its attributes. Some you can specify, others you can only view.

For example, the maximum message length that a queue can accommodate is defined by its MaxMsgLength attribute; you can specify this attribute when you create a queue. The DefinitionType attribute specifies how the queue was created; you can only display this attribute.

In IBM MQ, there are two ways of referring to an attribute:
  • Using its PCF name, for example, MaxMsgLength.
  • Using its MQSC command name, for example, MAXMSGL.
[z/OS]

Queue sharing groups

Queue managers that can access the same set of shared queues form a group called a queue sharing group (QSG), and they communicate with each other using a coupling facility (CF) that stores the shared queues. Note that a QSG is not strictly an object.

A shared queue is a type of local queue with messages that can be accessed by one or more queue managers that are in a queue sharing group. This is not the same as a queue being shared by more than one application, using the same queue manager.

Queue sharing groups have a name of up to four characters. The name must be unique in your network, and must be different from any queue manager names.
Important: Shared queues and queue sharing groups are supported only on IBM MQ for z/OS.

See Shared queues and queue sharing groups for more information.

System default objects

System default objects are a set of object definitions that are created automatically whenever a queue manager is created. You can copy and modify any of these object definitions for use in applications at your installation.

Default object names have the stem SYSTEM; for example, the default local queue is SYSTEM.DEFAULT.LOCAL.QUEUE, and the default receiver channel is SYSTEM.DEF.RECEIVER. You cannot rename these objects; default objects of these names are required.

When you define an object, any attributes that you do not specify explicitly are copied from the appropriate default object. For example, if you define a local queue, those attributes that you do not specify are taken from the default queue SYSTEM.DEFAULT.LOCAL.QUEUE.

See System and default objects for more information.