A consistency group is a group of volumes that supports capabilities such as creating a snapshot of all of its member volumes at the same point-in-time with a write-fence, thus ensuring a consistent image of the volumes at that time.

Applications with datasets scoped to a single volume may have its contents saved to a snapshot, replicated or cloned in a crash-consistent manner implicitly with corresponding native ONTAP volume-granular operations. Applications with datasets spanning a group of multiple volumes must have such operations performed on the group, typically by first fencing writes to all the volumes in the group, flushing any writes pending in queues, execute the intended operation, viz., take snapshot of every volume in the group and when that is complete, unfence and resume writes. A consistency group (consistency group) is the conventional mechanism for providing such group semantics.