To create a new consistency group, the change recording data structure 310, indicating data written, i.e., updated, while copying written data for the current consistency group being formed, is merged with the out-of-synch data structure 308, which does not indicate tracks to copy after the current consistency group is completed. After the merging, the change recording data structure 310 is cleared to record new updates for a next consistency group while the data indicated as changed in the out-of-synch data structure 308 is being copied to the target volume 306 to form the current consistency group.

FIG. 4 illustrates an embodiment of an instance of a target mirror copy relationship 400_i maintained at the target server 400₂, which may include a mirror copy identifier 402 identifying the mirror copy created by a source copy manager 412₁; a source volume 404, such as all or part of a source volume 104₁, from which data is copied; and a target volume 406, such as all or part of a target volume 104₂, to which data is copied from the source volume 404.