The mirror copies 300, 400 and point-in-time copies 500 may be implemented with copy technology known in the art, such as IBM? FlashCopy?, IBM? Metro Mirror?, IBM? Global Mirror?, and mirror and snapshot technology provided from other vendors. (IBM, FlashCopy, Metro Mirror, and Global Mirror are registered trademarks or common law marks throughout the world.

A point-in-time copy 500 replicates data in a manner that appears instantaneous, and any actual data transfers to the copy volume are deferred to a later time when the data in the target volume 104₂ in the point-in-time copy 108 is subject to a write following the creation of the point-in-time copy. The point-in-time copy appears instantaneous because complete is returned to the copy operation in response to generating the data structures 500 without copying the data. Point-in-time copy techniques typically defer the transfer of the data in the target volume 104₂ at the time the point-in-time copy relationship 500 was established to the point-in-time copy 108 until a write operation is requested to that data block on the target volume 104₂ following the point-in-time 504.