Before you can define and activate a policy, you must format a couple data set to hold the policy and ensure that the data set is available to the systems in the sysplex configuration that need it. You will create the following couple data sets:
Sysplex couple data set: stores information about its systems, the XCF groups and members running in the sysplex, and general status information. Each sysplex requires a sysplex couple data set.
Sysplex failure management (SFM) couple data set: holds the SFM policy, which allows you to define how system failures, signaling connectivity failures, and PR/SM reconfiguration actions are to be managed.
System logger (LOGR) couple data set: holds the policy that allows you to define logstream structure definitions.
Workload management (WLM) couple data set: holds the WLM policy, which allows you to define service goals for workloads.
Couple data set placement
The placement of couple data sets can improve performance, as well as availability. IBM recommends that you define separate volumes for the primary, alternate, and spare couple data sets. Place couple data sets on volumes that are attached to cached control units with the DASD fast write (DFW) feature. Although this recommendation applies to all couple data sets in any size sysplex, it is more critical the more systems you have in the sysplex. Those couple data sets most affected are the sysplex couple data set and the CFRM couple data set.
Place couple data sets on volumes that are not subject to reserve/release contention or significant I/O contention from sources not related to couple data sets (even if the I/O contention is sporadic).
IBM recommends that you define three data sets for each type of couple data set:
To ensure recovery, you should keep primary and alternate couple data sets on different volumes (volsers). Additionally, IBM recommends that backup or spare copies of the couple data sets be placed on a third volume.
If the primary data set fails, the alternate data set automatically becomes the primary and you can make the spare data set the alternate. You must define primary, alternate, and spare volumes in the wizard.
Use a volume that has sufficient space and specify from 1 to 6 characters. Do not use SMS-managed volumes for the couple data sets.
If you already have couple data sets defined, the wizard uses those names for the couple data sets in the panel. You must define all couple data sets in the wizard.