concurrent copy:    A hybrid point-in-time copy mechanism for which each copy is initially a changed block point-in-time copy (i.e., shares unmodified storage with its source), but over time becomes a split mirror copy (i.e., does not share any storage with its source) without changing the point in time at which the copy logically occurred, independent of whether and where modifications to the source or the copy subsequently occur. A concurrent copy occupies at least the amount of storage required to hold changed blocks and grows to occupy as much storage as the copy source.

See also: TBD