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:
- 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.