Planning signaling services in a sysplex

Signaling is the mechanism through which XCF group members communicate in a sysplex. In a multisystem sysplex, signaling can be achieved through:

Channel-to channel (CTC) communication connections, which can be:
- An ESCON® or FICON® channel operating in CTC mode
- The 3088 Multisystem Channel Communication Unit
A coupling facility (using coupling facility list structures)
A combination of CTC connections and list structures.

Full signaling connectivity is required between all systems in a sysplex; that is, there must be an outbound and an inbound path between each pair of systems in the sysplex.

To avoid a single point of signaling connectivity failure, IBM® recommends redundant connections between each pair of systems, through either CTC connections or coupling facility list structures.