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.

  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.

    Figure 1. Unshared FC channel to unshared FC channel
    Unshared FC channel to unshared FC channel
  2. 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.

    Figure 2. Unshared FC channel to shared FC channel
    Unshared FC channel to shared FC channel
  3. 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.

    Figure 3. Shared FC channel to unshared FC channel
    Shared FC channel to unshared FC channel
  4. 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.
    Figure 4. Shared FC channel to shared FC channel
    Shared FC channel to shared FC channel