Use space efficient FlashCopy® for copies that are short term, such as copies that are backed up to tapes. You can also use space efficient FlashCopy for copies that are kept long term, if there are few updates to the source and target volumes. Space efficient FlashCopy relationships are limited to full volume relationships. Thus, extent specifications are not supported.
You must specify NOCOPY for space efficient relationships. You can use space efficient volumes with all other FlashCopy functions, such as change recording and consistency groups.