CLOCKxx (time of day parameters)

CLOCKxx performs the following functions:

• Prompts the operator to initialize the time of day (TOD) clock during system initialization.
• Specifies the difference between the local time and Coordinated Universal Time (UTC).
• Controls the utilization of the IBM® Sysplex Timer (9037), which is an external time reference (ETR). Having all systems in your complex attached and synchronized to a Sysplex Timer ensures accurate sequencing and serialization of events.
• Provides the means of specifying that the Server time Protocol (STP) architecture is to be used in the sysplex. STP defines the method by which multiple servers maintain time synchronization.
• Allows an installation to set an acceptable time deviation for the TOD clock from an external time source. When the specified ACCURACY bounds are exceeded, an error message is issued so the problem can be corrected. See the section on setting the accuracy monitor service for the TOD clock in z/OS MVS Planning: Operations for more information.
• Along with the ACCURACY keyword, specify the ACCMONINTV keyword to set a user-defined timing interval when the TOD clock accuracy monitor service is to be processed.

The CLOCKxx member for a system that is a member of a multisystem sysplex must contain a specification of ETRMODE YES, STPMODE YES, or both. The system then uses the Sysplex Timer or STP to synchronize itself with the other members of the sysplex. The system uses a synchronized time stamp to provide appropriate sequencing and serialization of events within the sysplex.

For more information about CLOCKxx and the Sysplex Timer, see z/OS MVS Setting Up a Sysplex.