When disaster disables the source of a SnapMirror relationship, you can use the snapmirror resync command as part of a strategy to update the repaired source and reestablish the original configuration of the systems.
In this example, all data from the last scheduled SnapMirror Snapshot copy before the source was disabled and all the data written to systemB:vol/volB after it was made writable is preserved. Any data written to systemA:vol/volA between the last SnapMirror Snapshot copy and the time that systemA:vol/volA was disabled is not preserved.