The DQM channel control function

The channel control function provides the administration and control of message channels between WebSphere MQ for z/OS and remote systems. See Figure 28 for a conceptual picture.

The channel control function consists of panels, commands and programs, two synchronization queues, channel command queues, and the channel definitions. The following is a brief description of the components of the channel control function.

• The channel definitions are held as objects in page set zero or in DB2^(R), like other WebSphere MQ objects in z/OS.
• You use the operations and control panels or MQSC commands to:
  • Create, copy, display, alter, and delete channel definitions
  • Start and stop channel initiators and listeners
  • Start, stop, and ping channels, reset channel sequence numbers, and resolve in-doubt messages when links cannot be re-established
  • Display status information about channels
  • Display information about DQM

  In particular, you can use the CSQINPX initialization input data set to issue your MQSC commands. This can be processed every time you start the channel initiator. See the WebSphere MQ for z/OS Concepts and Planning Guide for information about this.

• There are two queues (SYSTEM.CHANNEL.SYNCQ and SYSTEM.QSG.CHANNEL.SYNCQ) used for channel re-synchronization purposes. You should define these with INDXTYPE(MSGID) for performance reasons.
• The channel command queue (SYSTEM.CHANNEL.INITQ) is used to hold commands for channel initiators, channels, and listeners.
• The channel control function program runs in its own address space, separate from the queue manager, and comprises the channel initiator, listeners, MCAs, trigger monitor, and command handler.
• For queue-sharing groups and shared channels, see Chapter 33, Preparing WebSphere MQ for z/OS for DQM with queue-sharing groups.
• For Intra-group queuing, see Chapter 37, Intra-group queuing