Hi
You need to re-sync the relationship in the other direction (in 7-mode there used to be "vol restrict" command to change a vold to DP, it's not needed in Cdot):
SnapMirror resync -source-path DR_SVM:DR_VOL -destination-path PROD_SVM:PROD_VOL
i suggest you do that right after breaking the relationship. to make sure nothing keep writing to Prod while the DR volume is writable (and leaves you with two datasets)
Gidi