Synchronized Time Source and the coupling facility

Improved processor and coupling facility link technologies inherent on the z17 necessitate more rigorous time synchronization tolerance for members of a parallel sysplex hosted by those models. To help ensure that any exchanges of time-stamped information between members of a sysplex observe the correct time ordering, time stamps are now included in the message-transfer protocol between the systems and the coupling facility.

Consequently, a coupling facility hosted by any z17 requires connectivity to the same synchronized time source as the other z/OS® systems in its parallel sysplex. If a member of its parallel sysplex is on the same server as the coupling facility, required connectivity is already provided to the synchronized time source. However, when a coupling facility is a resident of an z17, which does not include a member of the coupling facilities parallel sysplex, connectivity attached to the synchronized time source must be implemented.