Rebuild Duplex Established Phase

This phase applies to the duplexing rebuild process, not to the rebuild process. When the Rebuild Connect Phase ends, the system notifies each connector with a Rebuild Duplex Established event. During the Rebuild Duplex Established phase, connectors operate in duplex mode accessing both the old and new structures to ensure that both structures are fully synchronized. New connectors can request access to both structures, first to the old structure, and if successfully connected, then to the new structure. If the attempt to connect to the old structure is not successful, the system does not allow the user to connect to the new structure, and both structures remain in the Duplex Established phase. If the attempt to connect to the old structure is successful, but the connect to the new structure is not, MVS™ stops the duplexing process for the new structure.

The Rebuild Duplex Established phase is open-ended, that is, connectors can continue in duplex mode for as long as is required. At some point, MVS might determine that duplexing should be discontinued, or a connector or an operator might send a request to the system to end the Duplex Established phase. The request will specify which of the duplexed structures is to be kept — either by falling back to use the old structure or by switching forward to complete the rebuild process using the new structure.

If the request is to stop the duplexing and fall back to the old structure (KEEP=OLD), processing occurs as for stopping a non-duplexed structure rebuild. See Stopping a User-Managed Rebuild Process.
If the request is to stop the duplexing and switch to the new structure (KEEP=NEW), MVS marks the structure as “switch in progress” and delivers the Rebuild Switch event to all connectors. Before responding to this event, all connectors, including those who have connected while the switch is in progress, must quiesce duplexing rebuild and complete operations to the new structure. To confirm the completion of these activities, each connector issues IXLREBLD REQUEST=DUPLEXCOMPLETE. When the system has received the REQUEST=DUPLEXCOMPLETE request from all connectors, the Rebuild Duplex Complete Sync Point is reached and the Rebuild Duplex Established phase ends. Processing continues with the Rebuild Cleanup phase.