3DC cascade configuration using delta resync with three UR sites

You create a UR pair that connects the primary and secondary sites so that the remote copy system created with the host operation site and backup site can be created immediately if a failure or disaster occurs at the intermediate site. A UR pair that is created to make a triangle-shaped remote copy connection among the three sites is called UR delta resync pair. By creating a UR delta resync pair between the primary and secondary sites in advance, you can transfer the copying operations from between the primary and intermediate sites back to between the intermediate and secondary sites in a short time when the intermediate site failure is corrected, and the intermediate site is brought back online.

The following illustration shows the 3DC cascade configuration using delta resync with three UR sites.