Best practices for updating a coupling facility

IBM recommends following the best practices documented herein when upgrading a coupling facility. These procedures for upgrading a coupling facility use the most current and simplified options to ensure a successful upgrade. These steps are intended to help you avoid unexpected delays or outages to applications that are using structures in coupling facilities. It is suggested that you follow all of the steps in the procedures. When adhered to, the procedures are designed to maximize availability and reliability. The best practice procedures contained herein assumes that you want to keep the sysplex operational across the upgrade.

Note: In the context of this section, a "processor" is defined as a physical collection of hardware that consists of main storage, one or more central processors, timers, and channels, on which a coupling facility image resides.

The first procedure, "Push/pull" of a coupling facility or POR of a processor with a coupling facility, should be used for either of the following situations:

there is a “push/pull” of a CPC on which a coupling facility image resides
there is to be a power-on reset, POR, of the CPC on which the coupling facility image resides and there is a physical or logical change to the coupling facility.

A “push/pull” is defined as the replacement of one CPC containing a CF image with another CPC that will contain a replacement CF image. Physical changes to a coupling facility include the number of links, the control unit number, where the links physically connect. The logical change of a coupling facility refers to the coupling facility definition in the CFRM policy.

The next procedure, POR of a CPC with a Coupling Facility with no Physical or Logical Changes to the CF, also pertains to a POR of a CPC on which a coupling facility image resides. However, this procedure applies to the specific situation where there is to be a POR of a CPC on which a coupling facility resides and, across the POR, there are no physical or logical changes to the coupling facility.

Finally, Disruptive CF Upgrade documents the procedure for a disruptive coupling facility upgrade. The disruptive coupling facility upgrade procedure should be conformed to anytime the coupling facility image must be reactivated but the CPC on which the coupling facility resides is not going to be PORd. Most CFCC maintenance applications can be achieved concurrently. That is, the CF image does not need to be reactivated to pick up the new service level of CFCC. The reasons a CF image may need to be reactivated include: the rare disruptive coupling facility code change, change to CFCC image storage requirements, and activating a new Coupling Facility Release level that is typically delivered with a System z driver upgrade.

Caution: Failure to adhere to the recommended best practices may result in unexpected delays or outages to applications using structures in coupling facilities. Also, technical difficulties trying to obtain access to the new coupling facility may occur if any of the steps or sequence of steps is not properly followed.