Patent ID: 8285679

Claim:
A method of operating a copy function to create a point-in-time copy relationship, comprising: initiating a point-in-time copy function to create a new point-in-time copy relationship from a source volume comprising a first volume to a target volume comprising a second volume; detecting that the target volume of the new point-in-time copy relationship is a source volume of a first pre-existing point-in-time copy relationship having as a target volume a third volume; detecting that the target volume of the first pre-existing point-in-time copy relationship is a source volume of a second pre-existing point-in-time copy relationship having as a target volume a fourth volume; and creating a buffer point-in-time copy relationship having a source volume comprising the target volume of the first pre-existing relationship and a target volume comprising a fifth volume in response to detecting that the target volume of the new point-in-time copy relationship is the source volume of the first pre-existing point-in-time copy relationship and detecting that the target volume of the first pre-existing point-in-time copy relationship is the source volume of the second pre-existing point-in-time copy relationship, wherein the creating the buffer point-in-time copy results in a cascade of the first volume to the second volume, the second volume to the fifth volume, the fifth volume to the third volume, and the third volume to the fourth volume.