Auto-configuration

In the FICON® architecture, device level communication between a channel and control unit requires that a Logical Path is established between them. In the case of FICON CTC, one or two channels each talk to a two-sided control unit which is internal to the FICON channel. Therefore, two logical paths are required for a complete CTC connection.

The Local logical path is established across the internal link between the channel function and the CTC function on the same CHPID. The Remote logical path is established across the Fibre Channel link. This path connects the two CHPIDs through the switch in Figure 1 or can also be point-to-point. In the case of a single FICON channel used to configure LPAR to LPAR communication within a CPC, the channel establishes both the local and remote logical paths.

To define a FICON CTC connection, you must define two FICON CTC control units with control unit types of FCTC. The FICON channels negotiate with each other and only one of the channels will contain a single CTC control unit internal to the channel for the CTC connection. This negotiation is described as auto-configuration. Auto-configuration determines which FICON channel contains the CTC control unit for each connection and pair of logical paths. If only one of the channels is on a CPC that supports the FICON CTC control unit function, the FICON CTC control unit is always on that channel. If both channels are on a CPC that supports the FICON CTC control unit function, the channels perform load balancing to determine which channel will have the FICON CTC control unit. The channel with the fewest CTC logical paths will have the FICON CTC control unit for the connection. This balances the load that FICON CTC connections will place on each channel.