Planning for a Coupling Facility Shutdown

Before removing a CF from a Parallel Sysplex® configuration, whether for replacement or maintenance, consider the following:

Remove only one CF at a time from service. Perform maintenance for the CF during off-peak periods. Ensure structure preference lists in the CFRM active policy contain any alternate CFs to be used for structure rebuild (or duplexing).
Most configurations should have multiple coupling facilities installed for improved availability. Ensure that all systems currently using a structure in the CF to be removed have connectivity to the alternate CFs.
If the CF being removed contains an XCF signaling structure, ensure that a full set of redundant signaling paths are in place. For example, if a signaling connection consists of only a single signaling structure (and no CTC connections), signaling connectivity is lost during the structure rebuild process. The loss of signaling connectivity lengthens the time it takes to rebuild the signaling structure and might result in XCF timeouts,
XCF signaling structures should be rebuilt one at a time and not concurrent with any other structure rebuild. Note that REALLOCATE processing will rebuild structures one at a time.
If redundant signaling paths for all systems are not available during the maintenance procedure, consider increasing the following values in to prevent an XCF timeout:
- Use the SETXCF COUPLE command to change the system failure detection interval (INTERVAL). It might be necessary to also change this value in the SYS1.PARMLIB member COUPLExx.
- In a global resource serialization ring complex, use the SETGRS command to change the maximum tolerance time interval global resource serialization allows the RSA-message to return to a system (TOLINT . It may also be necessary to change this value in the SYS1.PARMLIB member GRSCNFxx .
If redundant signaling paths between all pairs of systems are not available during the maintenance procedure, it is recommended that SFM actions to remove a system for signaling connectivity failures be disabled, either by disabling SFM or by temporarily changing the SFM policy to specify CONNFAIL(NO) during the maintenance period.
Ensure that enough capacity (storage, CP cycles, link capacity, and structure IDs) exists on the alternate CFs.
If there is not enough capacity on the alternate CFs to accommodate all structures to be rebuilt, consider deleting structures (see Deleting structures). In particular, consider deleting the following structures:
- For XCF signaling structures, use CTC connections for XCF signaling and stop XCF signaling paths through the CF structures. See Deleting the XCF signaling structure.
- For JES2 structures, place the checkpoint on DASD and remove the CF structure. See Deleting the JES2 checkpoint structure.
- For RACF® structures, use RACF in non-data sharing mode, which will automatically delete the RACF structures. See Deleting the RACF database cache structures.
When using Server Time Protocol (STP) to maintain time synchronization, consider the effect of the reconfiguration on the Coordinated Timing Network (CTN). See the Server Time Protocol Implementation Guide redbook for more information.