Problem: a subset of members have lost connectivity (duplexed)

In a data sharing environment with duplexed structures, one or more members might lose connectivity to the coupling facility, while other members do not. This problem might happen if a link is detached between a system and the coupling facility.

This scenario assumes that the group buffer pool, lock, and SCA structures are duplexed. For a duplexed structure, the system will automatically fall out of duplexing when a member loses connectivity to one of the structure instances, and the system will use the structure instance with full connectivity in a simplexed state.

If DUPLEX(ENABLED) is specified in the CFRM policy, then the system will attempt to automatically reestablish duplexing, if another coupling facility exists that has full connectivity and that coupling facility exists in the structure's preference list. If DUPLEX(ENABLED) is specified, but no preferred and connected coupling facility exists, then the system will attempt to automatically reestablish duplexing when full connectivity is restored to the original coupling facility.

Symptom

The following messages will appear if the secondary group buffer pool structure is lost:

DSNB743 csect-name DUPLEXING IS BEING STOPPED FOR GROUP BUFFER POOL gbpname
			FALLING BACK TO PRIMARY,
			REASON = LOSSCONNSEC
			DB2 REASON CODE = xxxxxxxx

DSNB745 csect-name THE TRANSITION BACK TO SIMPLEX MODE HAS COMPLETED FOR
        GROUP BUFFER POOL gbpname

The following messages will appear if the primary group buffer pool structure is lost:

DSNB744 csect-name DUPLEXING IS BEING STOPPED FOR GROUP BUFFER POOL gbpname
			SWITCHING TO SECONDARY,
			REASON = LOSSCONNPRI
			DB2 REASON CODE = xxxxxxxx

DSNB745 csect-name THE TRANSITION BACK TO SIMPLEX MODE HAS COMPLETED FOR
        GROUP BUFFER POOL gbpname

System action

The duplexed group buffer pool, lock, and SCA structures will fall back to simplex when either copy of the duplexed structure is lost.

System programmer action

No action is required at this time.

If there are 2 coupling facilities originally: When the CF that failed is brought back online, the structures will duplex themselves automatically if DUPLEX(ENABLED) was specified as recommended in the CFRM policy.

If there are more than 2 coupling facilities specified in the preference list of the CFRM policy for the structure: The structure will duplex itself using the remaining coupling facilities if DUPLEX (ENABLED) was specified in the structure statement of the CFRM policy.

After all coupling facilities have been restored to service, you should issue the SETXCF START,REALLOCATE at a low time of activity, to ensure that the group buffer pools are restored to their preferred coupling facilities.