The channel initiator on z/OS
The channel initiator provides and manages resources that enable IBM® MQ distributed queuing. IBM MQ uses Message Channel Agents (MCAs) to send messages from one queue manager to another.
To send messages from queue manager A to queue manager B, a sending MCA on queue manager A must set up a communications link to queue manager B. A receiving MCA must be started on queue manager B to receive messages from the communications link. This one-way path consisting of the sending MCA, the communications link, and the receiving MCA is known as a channel. The sending MCA takes messages from a transmission queue and sends them down a channel to the receiving MCA. The receiving MCA receives the messages and puts them on to the destination queues.
In IBM MQ for z/OS®, the sending and receiving MCAs all run inside the channel initiator (the channel initiator is also known as the mover ). The channel initiator runs as a z/OS address space under the control of the queue manager. There can be only a single channel initiator connected to a queue manager and it is run inside the same z/OS image as the queue manager. There can be thousands of MCA processes running inside the channel initiator concurrently.
- Listeners
- These processes listen for inbound channel requests on a communications subsystem such as TCP, and start a named MCA when an inbound request is received.
- Supervisor
- This manages the channel initiator address space, for example it is responsible for restarting channels after a failure.
- Name server
- This is used to resolve TCP names into addresses.
- SSL tasks
- These are used to perform encryption and decryption and check certificate revocation lists.