System-managed coupling facility structure duplexing
A set of parallel sysplex architectural extensions is provided for support of system-managed duplexing of coupling facility structures for high availability. All three structure types, cache, list, and locking, can be duplexed using this architecture.
- Availability: Faster recovery of structures by having the data already in the second CF.
- Manageability and Usability: A consistent procedure to set up and manage structure recovery across multiple exploiters
- Cost Benefits: Enables the use of non-stand-alone CFs (for example, ICFs) for all resource sharing and data sharing environments.
Preparations for CF duplexing includes the requirement to connect coupling facilities to one another with coupling links. The required CF-to-CF connectivity is bi-directional, so that signals can be exchanged between the CFs in both directions. A single peer-mode coupling link between each pair of CFs can provide the required CF-to-CF connectivity; however, for high availability at least two peer-mode links between each pair of CFs are recommended.
While peer-mode CHPIDs cannot be shared between multiple coupling facility images, they can be shared between a single coupling facility image and one or more z/OS® images. At least two such links is recommended for high availability. In addition, ICR SR links can provide the ability to actually share the same physical link between multiple CF images. By defining multiple CHPIDs on the same physical ICR SR link and CE2 LR link, the individual CHPIDs can be defined for a single CF image while the physical link is being shared by multiple CF images.