You might break a SnapMirror relationship when a disaster impacts the source volume so that you can temporarily serve data from the destination volume. There are some considerations you should understand before breaking a SnapMirror relationship so that you can avoid issues.
This is evident when the SnapMirror relationship is part of a cascade and is the expected behavior. If, for example, you have a cascade from volume A to volume B and volume B to volume C, and you break the relationship between volume A and volume B. The relationship between volume B and volume C still exists. When a replication update from volume B to volume C occurs, volume B will lose the common Snapshot copy it has with volume A.
You can avoid this issue by creating your own Snapshot copy on the source that will not get deleted automatically, and then replicating it to the destination volume before breaking the relationship.