For both user-managed and system-managed duplexing rebuild, FORCE is allowed only during the Duplex Established phase when switch processing has not been requested. Otherwise, the FORCE request will fail.

User awareness of changes in the volatility state differs between user-managed and system-managed duplexing rebuild. In user-managed duplexing rebuild, the system presents the Volatility State Change event to inform the user of changes to either of the structure instances. In system-managed duplexing rebuild, the sytem presents the Volatility State Change event whenever the “composite” volatility state changes. For example, a duplexed structure is considered to be nonvolatile if either instance of the structure in nonvolatile. If a volatility state change affects one of the coupling facilities in which one of the structure instances is allocated, the system will report the Volatility State Change event to users.

A structure transitioning into and out of the Duplex Established phase could also result in a volatility state transition. Volatility state transitions caused by starting or stopping duplexing rebuild are reported to users through the Structure State Change Notification event.

An “out of synch” condition applies to system-managed duplexing rebuild only. When a command that has been duplexed detects an “out of synch” condition, the integrity of the entire structure is at risk and therefore both instances of the structure are considered to have failed. The system-managed duplexing rebuild will be stopped and a Structure Failure event will be delivered.