Notes on delta resync
When a UR pair has not been suspended and resynchronized for a long time, the data in the restore journal might exceed 70% of capacity. If this happens, old journal data is automatically deleted. In this case, the P-VOL and S-VOL are not synchronized completely by just copying the data, and delta resync will fail. In case of delta resync failure, resynchronize the UR pair.
Journal data might be deleted in the following cases, even if the data in the restore journal does not exceed 70% of capacity:
When you update the P-VOL after resynchronizing the GAD pair.
When you update the P-VOL after resynchronizing the UR pair between the primary site and UR secondary site.
When retry-processing occurs because of a delay of the P-VOL update.
When the update of a GAD S-VOL is delayed.
If the pair status of the UR delta resync pair does not change after the delta resync operation, the prerequisites for delta resync might not be satisfied. Review the prerequisites for the pair status of the GAD pair, UR pair, and UR delta resync pair.