Virtual Channel-to-Channel Adapters

A virtual channel-to-channel adapter (3088) is defined for a virtual machine through a SPECIAL statement in its z/VM® directory entry, the DEFINE CTCA command, or the DEFINE 3088 command. You must specify the virtual device number to be assigned to the virtual channel-to-channel adapter. The user ID of the virtual machine allowed to connect with the virtual channel-to-channel adapter through the COUPLE command is optional.

A virtual channel-to-channel adapter can be defined whether or not a real channel-to-channel adapter is present in the real machine in which CP runs. This facility can be used to test multisystem operating systems and configurations (for example, multiple z/OS®/JES3 systems) using only one real machine. It can also be used in a multisystem environment to perform multisystem operating system testing or new release testing concurrent with usual production operations.

Figure 1 illustrates a z/OS/JES3 multisystem configuration consisting of two real machines in which both z/OS/JES3 system testing and production work are being done. CP simulates the existence of two z/OS/JES3 configurations. CP runs in one real machine to control the operation of three virtual machines.

Two of the virtual machines are connected by a virtual channel-to-channel adapter to form the two processors in the z/OS/JES3 configuration that is being used for testing. The CP COUPLE command must be entered to connect these two virtual machines by the virtual channel-to-channel adapter defined for each virtual machine.

The third virtual machine is connected to the second real machine by a real channel-to-channel adapter to form the processors of the second z/OS/JES3 configuration, which is doing production work. While CP can be used within a z/OS/JES3 multiprocessing configuration, as shown, CP itself does not support loosely-coupled real-machine multiprocessing configurations.