Duplexing rebuild monitoring

When DUPLEX(ENABLED) is specified for a structure in the CFRM active policy, the system will attempt to initiate duplexing (either user-managed or system-managed) for those eligible structures that are not currently duplexed. Note that user-managed duplexing rebuild, which applies only to cache structures, will be given precedence over system-managed duplexing rebuild when the structure exploiter supports both of these processes.

The conditions under which the system will attempt to initiate a duplexing rebuild are:

Occurrence of a connect to a structure
Occurrence of a disconnect
Change in the CFRM policy
Occurrence of a FORCE to a structure
System gains connectivity to a coupling facility
First system in a sysplex gains access to a coupling facility
Reconciliation (comparison) of a coupling facility's structure contents to a CFRM policy contents

Conditions that apply only to system-managed duplexing rebuild are:

Gain of CF-to-CF link connectivity
Issuance of a PSWITCH command to a CFRM couple data set that supports SMDUPLEX

Additionally, when DUPLEX(ENABLED) is specified for a structure in the CFRM active policy that is not duplexed, the system will set up a monitor to periodically check for the following conditions:

Completion of a rebuild or duplexing rebuild
Release of structure dump serialization
Deallocation of a structure
Completion of structure alter or contraction
Reduction in the size of the coupling facility dump space

When coupling facility resources become available as a result of one of these events listed above, such that a structure that previously could not be duplexed because of a lack of resources can now be duplexed, the system will eventually (but not immediately) attempt to duplex one or more structures using the newly available resources. The timing is dependent on that of the periodic monitoring.

When any of the conditions listed occurs, including those for which the system is periodically monitoring, the system will evaluate the feasibility of starting a duplexing rebuild of the appropriate type (user-managed or system-managed). If it appears that a duplexing rebuild cannot be initiated for a structure, given current conditions, the system will issue the following messages:

Message IXC574I is issued to the hardcopy log to document why starting a duplexing rebuild was not deemed feasible.
Message IXC538I is issued to the console to indicate the reason why the duplexing rebuild process could not be initiated. This message might be issued repeatedly due to the system's periodic monitoring of structures that specify DUPLEX(ENABLED) in the CFRM active policy. The installation might need to consider making configuration changes or taking other actions in order to allow duplexing to be started for the structure. It might also be appropriate to change the CFRM policy from DUPLEX(ENABLED) to either DISABLED or ALLOWED until the configuration changes can be made.

MVS™ will stop a duplexing rebuild process under the following conditions:

For user-managed duplexing rebuild, if the CFRM policy is changed such that one of the coupling facilities in which the duplexed pair of structures is allocated is removed from the preference list, the duplexing rebuild is stopped.
For both user-managed and system-managed duplexing rebuild, if the CFRM policy for DUPLEX is changed to DISABLED, the duplexing rebuild is stopped. Other policy changes such as preference list, structure size, etc. will not result in system-managed duplexing rebuild being stopped, but may result in a change becoming pending against the duplexed structure.

Once a duplexing rebuild is stopped, the following differences exist between user-managed and system-managed duplexing rebuild:

For user-managed duplexing rebuild, pending policy changes do not prevent user-managed duplexing rebuild from starting. After the stop process completes, user-managed duplexing rebuild will be started again and the pending policy changes will take effect when the new structure is allocated.
For system-managed duplexing rebuild, pending policy changes prevent system-managed duplexing rebuild from starting. Only a change to the DUPLEX setting takes effect immediately; if other changes cause the CFRM policy to become pending, system-managed duplexing rebuild cannot be started until the pending policy change for the structure takes effect.