Duplexing requirements

To achieve high availability for SCA, lock, and group buffer pool structures across many types of failures, three conditions must be met.

For duplexing to work, the following conditions must be true:
  • The CFRM policy preference list for the group buffer pool structure that you want to duplex must contain at least two coupling facilities with a CFLEVEL of 5 or higher. All members of the data sharing group must have physical connectivity to both coupling facilities in which the primary and secondary structures reside.

    If you are going to do automatic reduplexing, you need three coupling facilities that are physically connected to members of the data sharing group.

  • At least one member must be actively connected to the group buffer pool structure.
  • The group buffer pool must be defined with GBPCACHE(YES), the default.

For asynchronous duplexing of the lock structure, the CFRM couple data set needs to support asynchronous duplexing. To provide that support, add the following item to the CFRM couple data set parameters in the job that runs the format utility:

ITEM NAME(ASYNCDUPLEX) NUMBER(1)
Important: Include this item only when the coupling facility level is CFLEVEL 21 or higher, and the z/OS® system level is Version 2.2 with the PTF for APAR OA47796, or later versions.