FICON CTC control unit
The CTC control unit section in a FICON® channel can consist of multiple CTC control units. A CTC control unit is a two-sided control unit. One side is internal to the FICON channel that is providing the CTC control unit functions. The other side is connected to another FICON channel on a FICON interface. Each side is configured individually to its corresponding channel as a CTC control unit and is accessed independently by its corresponding channel. Each separately configured control unit represents one side of a two-sided CTC control unit in the FICON channel. See Figure 1.
- When an unshared FICON channel
(FC) with integrated CTC function is connected to another unshared
FC channel, only one CTC control unit can be configured for the CTC
connection. The two-sided control unit is used between the partitions
owning the FC channel with integrated CTC function and the other FC
channel.
In Figure 1, the CTC control unit 1 is configured for the CTC connection between FC channel x (with integrated CTC function) on System A and FC channel x on System B. CTC control unit 2 is configured for the CTC connection between FC channel x on System A and FC channel y on System B. CTC control unit 3 is configured for the CTC connection between FC channel x on System A and FC channel z on System B.
- When an unshared FC channel with integrated CTC function is connected
to a shared FC channel, a two-sided control unit can be configured
between the partition owning the FC channel with integrated CTC function
and each partition sharing the other FC channel.
In Figure 2, three CTC control units can be configured between LP2A in System A and each partition in System B.
- When a shared FC channel with integrated CTC function is connected
to an unshared FC channel, a two-sided control unit can be configured
between each partition sharing the FC channel with integrated CTC
function and the partition owning the unshared FC channel.
In Figure 3, three CTC control units can be configured between each partition in System A and LP2B in System B.
- When a shared FC channel with integrated CTC function is connected
to another shared FC channel, a two-sided CTC control unit can be
configured between each partition sharing the FC channel with integrated
CTC function and each partition sharing the other FC channel. In Figure 4, only three CTC control units need to be configured for the CTC connection between System A and System B. CTC control unit (CU) 1 is configured for the CTC connections between all logical partitions accessing FC channel x with integrated CTC function on System A and LP1B on System B. CTC CU 2 is configured for the CTC connections between all logical partitions accessing FC channel x with integrated CTC function on System A and LP2B on System B. CTC CU 3 is configured for the CTC connections between all logical partitions accessing FC channel x with integrated CTC function on System A and LP3B on System B.