A persistent FlashCopy relationship is one that does not end when the background physical copy ends. The relationship persists until it is explicitly withdrawn.
Persistent FlashCopy overrides normal FlashCopy processing and allows a FlashCopy relationship to stay active until it is explicitly withdrawn. Normally, a FlashCopy relationship is automatically withdrawn when the background physical copy ends.
Designating that a FlashCopy relationship be persistent can help protect against inadvertent updates of recently created target volumes. For example, if a source volume is regularly copied to alternating target volumes (thereby ensuring that a complete copy of the source volume is always available), the persistent relationship identifies the target volume for the most recently completed FlashCopy.
This FlashCopy procedure presents a possible exposure for mistakes. For instance, if the FlashCopy operation (step 2 of the FlashCopy procedure) is mistakenly performed from Volume A to Volume B rather than from Volume A to Volume C, the result could be data that overwrites the original point-in-time copy in volume B.
The use of the persistent FlashCopy function requires that the FlashCopy relationship is explicitly withdrawn before another FlashCopy operation can be performed. While this restriction does not guarantee that a point-in-time copy cannot be overwritten by mistake, it does provide an extra measure of security.