In a sysplex, you can direct a message to one or more systems for processing. You can control message routing to consoles in the sysplex through the MSCOPE keyword on the CONSOLE statement for MCS or SMCS consoles. For extended MCS consoles, you can use RACF® or MCSOPER to specify MSCOPE values. (See Table 1.) Operators can use the VARY command to control MSCOPE. Specifying MSCOPE allows the console to receive messages from one or more systems in the sysplex.

Regardless of the console MSCOPE value, the sysplex can direct messages in the form of command responses to the system where the console that issued the command is attached. For example, a console on SYA that issues a DISPLAY command for other consoles on SYB can expect to receive the message display in response to the command. For a subsystem-allocatable console, the sysplex can deliver a message to the subsystem where the console is allocated. Thus, a subsystem console on SYA can receive messages intended for the console even if the messages originated on SYB.

On the system that issues the message, the message flow occurs as it does for a single system. If the message flows to other systems in the sysplex, sysplex services directs the message to the subsystems for processing, but the message bypasses the message processing exits and the hardcopy log on the target systems.

The following summarizes message flow through a sysplex:

1. A program issues a WTO or WTOR message.
2. The message processing exits on the system that issues the message get control.
3. The subsystems can receive the message on the system that issues the message.
4. Hardcopy log processing on the system that issues the message can record the message. CNZ_MSGTOSYSLOG exit is invoked during the hardcopy log processing.
5. CNZ_WTOMDBEXIT exit receives the message. See z/OS MVS Installation Exits for more information.
6. Sysplex services directs the message to the other systems in the sysplex.
7. The subsystems on each receiving system can receive the message.
8. The MCS, SMCS and extended MCS consoles on the appropriate system can select the message for display.

As a result of this message flow in a sysplex, message processing that occurs through exits is possible only on the system that issues the message. You need to keep this in mind when you plan your installation exits for messages. Similarly, the hardcopy recording of the message occurs only on the issuing system.

On the other hand, subsystems like NetView® can receive the message on both the issuing system and any receiving system where NetView is installed. You can route messages to NetView on any system in order to control message automation for the system, but the NetView subsystems must coordinate automation for the sysplex based on the scope of the message flow to systems in a sysplex. (For planning automation using NetView, see NetView Automation: Planning.)