Advantages of implementing signaling through list structures

Implementing signaling through coupling facility list structures provides significant advantages in the areas of systems management and recovery and, thus, provides enhanced availability for sysplex systems.

While a signaling path defined through CTC connections must be exclusively defined as either outbound or inbound, you can define a coupling facility list structure so that it is used for both outbound and inbound signaling paths, and MVS™ automatically establishes the paths. For example, if you define a list structure for outbound message traffic, MVS automatically establishes a signaling path with every other system that has the structure defined for inbound message traffic. Similarly, if you define a list structure for inbound traffic, MVS automatically establishes a signaling path with every other system that has the structure defined for outbound traffic.

Because a single list structure can be defined for both inbound and outbound traffic, you can use the same COUPLExx parmlib member for each system in the sysplex. A CTC connection, in contrast, cannot be defined to a single system as both inbound and outbound. Therefore, with CTCs, you must specify a unique COUPLExx member for each system in the sysplex or configure your systems so that they can use the same COUPLExx member by overspecifying the number of devices for signaling paths and tolerating failure messages related to unavailable devices and other configuration errors.

Implementing signaling through coupling facility list structures also enhances the recovery capability of signaling paths and reduces the amount of operator intervention required to run the sysplex.