Patent ID: 8892834

Claim:
A method for performing a write to a volume x in a cyclic point-in-time-copy architecture, the method comprising: determining whether the volume x has a child volume, wherein each of the volume x and the child volume have a target bit map (TBM) associated therewith; determining whether the TBMs of both the volume x and the child volume are set: if the TBMs are set, finding a higher source (HS) volume from which to copy data to the child volume, wherein finding the HS volume comprises finding a source volume associated with the volume x, determining a downstream mapping relationship between the source volume and the volume x, and determining if an upstream mapping relationship from the source volume was created after the downstream mapping relationship, wherein the source volume is determined to be the HS volume if the upstream mapping relationship from the source volume was created after the downstream mapping relationship; determining whether the HS volume and the child volume are the same volume; copying the data from the HS volume to the child volume if the HS volume and the child volume are not the same volume; and performing the write on the volume x.