CTCM group devices
The CTCM device driver requires two I/O subchannels for each interface, a read subchannel and a write subchannel.
Figure 1 illustrates the I/O subchannel interface. The device bus-IDs that correspond to the two subchannels must be configured for control unit type 3088.
The device bus-IDs that correspond to the subchannel pair are grouped as one CTCM group device. There are no constraints on the device bus-IDs of read subchannel and write subchannel. In particular, it is possible to group non-consecutive device bus-IDs.
On the communication-peer operating system instance, read and write subchannels are reversed. That is, the write subchannel of the local interface is connected to the read subchannel of the remote interface and vice versa.