To allow system-managed duplexing rebuild in a sysplex, the installation must do the following:

1. Determine which structure exploiters support system-managed duplexing. Evaluate the necessity or the desirability of using the system-managed duplexing rebuild function on a structure-by-structure basis for each subsystem.
2. Migrate at least one system to z/OS® R2 before making the necessary coupling facility configuration changes. The DISPLAY command in z/OS R2 has been enhanced to allow you to display the CF-to-CF link connectivity, thus easing your ability to establish this connectivity.

   System-managed duplexing rebuild requires that the CFCC be at CFLEVEL 11 or higher and that CF-to-CF link connectivity be established between any pair of coupling facilities in which duplexed structures are to be allocated. For highest availability, it is recommended that the CF links be redundant, that is, more than one link in each direction. Prior to IBM eServer zSeries 900, separate sender and receiver links between coupling facilities were required. With the zSeries, coupling facilities can be connected with a single bidirectional link. As recommended, more than one of these links should be provided for higher availability.

3. Migrate all systems to z/OS Release 2.
4. Format CFRM couple data sets (primary and alternate) to support system-managed duplexing rebuild (include SMDUPLEX statement in IXCL1DSU). Bring the new couple data sets into use by adding one as a new alternate, PSWITCH to make it the primary, and then bring the second into the configuration as the alternate.

   RECOMMENDATION FOR AVOIDING SYSPLEX-WIDE IPL:

   Be aware that once these CFRM couple data sets that support system-managed duplexing rebuild are in use, no systems at a release lower than z/OS V1R2 will be able to use the CFRM function in the sysplex. Also note that if it is necessary to revert or fallback to a CFRM couple data set that does not have the capability of supporting system-managed duplexing rebuild, a sysplex-wide IPL will be required for all systems using the CFRM function. (However, it should not really ever be necessary to fall back from a CFRM couple data set that supports SMDUPLEX to one that does not. An alternative to doing this would simply be to disable duplexing for structures by changing the policy to one that specifies or defaults to DUPLEX(DISABLED) for the appropriate structures, or some desired subset of structures.)

5. Evaluate the effectiveness of enabling the structure for system-managed duplexing rebuild. For each structure that you have decided to use system-managed duplexing rebuild, migrate the exploiting subsystem or product to the level that supports system-managed duplexing rebuild. IBM® recommends that you do not define any structures in your CFRM policy as enabled for duplexing until the exploiting subsystem has been upgraded to the duplexing-capable level on all systems in the sysplex. While a structure is duplexed, downlevel connectors that do not support system-managed duplexing rebuild will be unable to connect to the duplexed structure.

   Create or modify a CFRM policy with the IXCMIAPU utility to enable the structure for system-managed duplexing rebuild (DUPLEX keyword) and determine the placement of the duplexed structures (preference list). Start the policy to make it the active CFRM policy in the sysplex.

   Continue this process on a structure-by-structure basis until all structures intended to be enabled for system-managed duplexing rebuild have been deployed.

   Note that the decision to allow or enable system-managed duplexing rebuild for each structure should be made on a subsystem or product basis. The installation can thus ensure that the appropriate software levels are in place to support system-managed duplexing rebuild on all systems, that sufficient coupling facility resources are available to support the duplexing workload for the structure, and that any performance considerations associated with duplexing the structure have been evaluated.

Once system-managed duplexing rebuild is operational in the sysplex, it is also the responsibility of the installation to monitor structure placement and performance and make any necessary tuning changes.

Refer to Migration steps to enable system-managed duplexing of logger structures for migration steps that you must take to enable system-managed duplexing of Logger structures.