Set up communications with other queue managers
This section describes the IBM MQ for z/OS preparations we need to make before we can start to use distributed queuing.
To define your distributed-queuing requirements, we need to define the following items:
- Define the channel initiator procedures and data sets
- Define the channel definitions
- Define the queues and other objects
- Define access security
To enable distributed queuing, we must perform the following three tasks:
- Customize the distributed queuing facility and define the IBM MQ objects required as described in Defining system objects and Preparing to customize queue managers on z/OS.
- Define access security as described in Security considerations for the channel initiator on z/OS .
- Set up your communications as described in Set up communication for z/OS.
If we are using queue sharing groups, see Distributed queuing and queue sharing groups.
See the following sections for additional considerations for using distributed queuing with IBM MQ for z/OS.
Operator messages
Because the channel initiator uses a number of asynchronously operating dispatchers, operator messages might occur on the log out of chronological sequence.
Channel operation commands
Channel operation commands generally involve two stages. When the command syntax has been checked and the existence of the channel verified, a request is sent to the channel initiator. Message CSQM134I or CSQM137I is sent to the command issuer to indicate the completion of the first stage. When the channel initiator has processed the command, further messages indicating its success or otherwise are sent to the command issuer along with message CSQ9022I or CSQ9023I. Any error messages generated could also be sent to the z/OS console.
All cluster commands except DISPLAY CLUSQMGR, however, work asynchronously. Commands that change object attributes update the object and send a request to the channel initiator. Commands for working with clusters are checked for syntax and a request is sent to the channel initiator. In both cases, message CSQM130I is sent to the command issuer indicating that a request has been sent. This message is followed by message CSQ9022I to indicate that the command has completed successfully, in that a request has been sent. It does not indicate that the cluster request has completed successfully. The requests sent to the channel initiator are processed asynchronously, along with cluster requests received from other members of the cluster. In some cases, these requests must be sent to the whole cluster to determine if they are successful or not. Any errors are reported to the z/OS on the system where the channel initiator is running. They are not sent to the command issuer.
Undelivered-message queue
A Dead Letter handler is provided with IBM MQ for z/OS. See The dead-letter queue handler utility (CSQUDLQH) for more information.
Queues in use
MCAs for receiver channels can keep the destination queues open even when messages are not being transmitted. This behavior results in the queues appearing to be 'in use'.
Security changes
If we change security access for a user ID, the change might not take effect immediately. (See one of Security considerations for the channel initiator on z/OS , Profiles for queue security, and Implement your ESM security controls for more information.)
Communications stopped - TCP
If TCP is stopped for some reason and then restarted, the IBM MQ for z/OS TCP listener waiting on a TCP port is stopped.
Automatic channel-reconnect allows the channel initiator to detect that TCP/IP is unavailable and to automatically restart the TCP/IP listener when TCP/IP returns. This automatic restart alleviates the need for operations staff to notice the problem with TCP/IP and manually restart the listener. While the listener is out of action, the channel initiator can also be used to try the listener again at the interval specified by LSTRTMR in the channel initiator parameter module. These attempts can continue until TCP/IP returns and the listener successfully restarts automatically. For information about LSTRTMR, see Security concepts on z/OS and Distributed queuing messages (CSQX...).
Communications stopped - LU6.2
If APPC is stopped, the listener is also stopped. Again, in this case, the listener automatically tries again at the LSTRTMR interval so that, if APPC restarts, the listener can restart too.
If the Db2 fails, shared channels that are already running continue to run, but any new channel start requests fail. When the Db2 is restored new requests are able to complete.
z/OS Automatic Restart Management (ARM)
Automatic restart management (ARM) is a z/OS recovery function that can improve the availability of specific batch jobs or started tasks (for example, subsystems). It can therefore result in a faster resumption of productive work.To use ARM, we must set up your queue managers and channel initiators in a particular way to make them restart automatically. For information, see Use the z/OS Automatic Restart Manager (ARM).
- Defining IBM MQ objects
Use one of the IBM MQ command input methods to define IBM MQ objects. Refer to the information within this topic for further details about defining these objects.- Monitor and control channels on z/OS
Use the DQM commands and panels to create, monitor, and control the channels to remote queue managers.- Set up communication for z/OS
When a distributed-queuing management channel is started, it tries to use the connection specified in the channel definition. To succeed, it is necessary for the connection to be defined and available. This section explains how to define a connection.- Preparing IBM MQ for z/OS for DQM with queue sharing groups
Use the instructions in this section to configure distributed queuing with queue sharing groups on IBM MQ for z/OS.Parent topic: Configure queue managers on z/OS
Related concepts
- Set up IBM MQ for z/OS
- Monitor and control channels on z/OS
- Set up communication for z/OS
- Preparing IBM MQ for z/OS for DQM with queue sharing groups
- Set up communication for IBM MQ for z/OS using queue sharing groups
Related tasks