CTC communication and connection

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A FICON® channel-to-channel (CTC) connection consists of an input/output (I/O) device that is used by a program in one system to communicate with a program in another system. A CTC communication is established between two programs when the adapter is selected to respond to channel-command words (CCWs) that are issued by the channels in the CTC connection.

FICON CTC increases the connectivity options for customers. Now, each of any two systems that have at least one FICON channel connected to the network can have CTC connections set up between them with no additional cost. Customers no longer have to dedicate channel path (CHPID) resources to the CTC function. In the Fibre Connection (FICON) channel I/O interface environment, a stand-alone CTC adapter unit is not used to provide the switching function. The switching function is provided by the FICON Director. CTC connections between channels can be made by going through a FICON Director. The CTC adapter function is implemented logically between connecting channels and resides in the FICON channel.

The fibre channel path functions as both a channel and a channel-to-channel at the same time. It provides self configuration and load balancing of the CTC function among FICON channel paths, including proper configuration when the target channel does not have an integrated CTC.

FICON CTC connections require that at least one end of the connection be on the following CPC which supports the FICON CTC control unit function:

  • IBM zSystems and LinuxONE general purpose models at EC J10638 or later.

The other end of the FICON CTC connection can be on any CPC that supports FC channel paths. If neither FC channel path is on a CPC listed above, no FICON CTC connection will be established and the CTC devices will be unusable.

FICON CTC acts as a dual-sided control unit, providing control unit function for both the local inboard channel and an outboard channel on the other side of the fibre channel network. CTC function does not access storage or any system facilities.