IBM z/OS manual System-Managed CF Structure Duplexing

•Dynamic ICF Expansion: Dynamic ICF expansion pro- vides value by providing extra CF capacity when there are unexpected peaks in the workload or in case of loss of CF capacity in the cluster.

–ICF Expansion into shared CPs. A CF partition running with dedicated ICFs needing processing capacity beyond what is available with the dedicated CP ICFs, can “grow” into the shared pool of application CPs being used to execute S/390 applications on the same server.

–ICF Expansion into shared ICFs. A CF partition run- ning with dedicated ICFs can “grow” into the shared pool of ICFs in case the dedicated ICF capacity is not suffi cient. The resulting partition, an “L-shaped” LPAR, will be composed of both shared ICF and dedicated ICF processors, enabling more effi cient utilization of ICF resources across the various CF LPARs.

System-Managed CF Structure Duplexing

System-Managed Coupling Facility (CF) Structure Duplex- ing provides a general purpose, hardware-assisted, easy- to-exploit mechanism for duplexing CF structure data. This provides a robust recovery mechanism for failures such as loss of a single structure or CF or loss of connectivity to a single CF, through rapid failover to the backup instance of the duplexed structure pair.

Benefi ts of System-Managed CF Structure Duplexing include:

•Availability

Faster recovery of structures by having the data already there in the second CF, dramatically reducing the time and processing required for structure rebuilds. System- Managed Duplexing also provides basic recovery for many structures that have no simple means to recover data for failed structures, failed CFs, and losses of CF connectivity.

•Manageability and Usability

A consistent procedure for duplexing does not “set up” structures and manage structures across multiple exploiters.

•Reliability

A common framework provides less effort on behalf of the exploiters, resulting in more reliable subsystem code.

•Cost Benefi ts

Facilitates the use of non-standalone CFs (e.g. ICFs) for data sharing environments in addition to resource shar- ing environments.

•Flexibility

The diagram below represents creation of a duplexed copy of the structure within a System-Managed CF Duplexing Confi guration.

z/OS ICF

z800/z900/z990/G5/G6

ICF z/OS

z800/z900/z990/G5/G6

A robust failure recovery capability

Note: An example of two systems in a Parallel Sysplex with CF Duplexing

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