Space efficient FlashCopy® refers to a FlashCopy relationship for which the target volume is a space efficient volume. With space efficient FlashCopy, the amount of physical space consumed by the target volume is limited to the minimum amount of space required to maintain the copy.
Fully provisioned volumes are volumes for which all of the physical space is allocated when the volume is created.
Initially, repository volumes are fully provisioned volumes. For space efficient volumes, physical space is allocated on a track basis. When data is written to a space efficient volume, a track of physical space is taken from the segments assigned to a repository volume. This track of physical space is used to hold the data for the space efficient volume. A repository volume provides the physical space for multiple space efficient volumes.
When a track on the source volume of any FlashCopy relationship is updated, the current version of the track must be copied to the target device before the update can be destaged on the source device. For a space efficient FlashCopy, the current version of the track is written to the space taken from the repository volume. This track is assigned to the space efficient volume. Thus, the amount of physical space consumed by the target volume of a space efficient FlashCopy relationship is limited to the minimum amount of space required to maintain the copy.
Space Efficient FlashCopy refers to a FlashCopy relationship for which the target volume is a space efficient volume. A repository volume provides the physical space for multiple space efficient volumes.
As tracks are destaged for space efficient volumes, storage for the tracks is obtained from the segments assigned to the repository volumes. The data for a space efficient volume is stored on the repository volume, but the data is only accessible from the space efficient volume. The host does not have access to the repository volume.
For information on limitations that apply to space efficient FlashCopy, see Limitations to space efficient FlashCopy.