IBM DS8000 User Manual page 137

Fast reverse
Reverses the FlashCopy relationship without waiting for the finish of the
background copy of the previous FlashCopy. This option applies to the
Global Mirror mode.
Inhibit writes to target
Ensures that write operations are inhibited on the target volume until a
refresh FlashCopy operation is complete.
Multiple Relationship FlashCopy
Allows a source volume to have multiple target volumes at the same time.
Persistent FlashCopy
Allows the FlashCopy relationship to remain even after the FlashCopy
operation completes. You must explicitly delete the relationship.
Refresh target volume
Provides the ability to "refresh" a FlashCopy relationship, without
recopying all tracks from the source volume to the target volume.
Reverse restore
Reverses the FlashCopy relationship and copies data from the target
volume to the source volume.
Reverse FlashCopy relationships
The direction of a FlashCopy relationship can be reversed, where the volume that
was previously defined as the target becomes the source for the volume that was
previously defined as the source (and is now the target). The data that has changed
is copied to the volume previously defined as the source.
You can reverse a FlashCopy relationship if you want to restore a source volume
(Volume A) to a point in time before you performed the FlashCopy operation. In
effect, you are reversing the FlashCopy operation so that it appears as though no
FlashCopy operation ever happened. Keep in mind that the background copy
process of a FlashCopy operation must complete before you can reverse volume A
as the source and volume B as the target.
There might be certain circumstances when you might want to reverse an original
FlashCopy relationship. For example, suppose you create a FlashCopy relationship
between source volume A and target volume B. Data loss occurs on source volume
A. To keep applications running, you can reverse the FlashCopy relationship so
that volume B is copied to volume A.
Note: A fast reverse option that applies to a Global Mirror operation allows a
FlashCopy relationship to be reversed without waiting for the background
copy of a previous FlashCopy relationship to finish. A Global Mirror
operation is based on existing Global Copy and FlashCopy operations at the
target site.
Figure 10 on page 110 illustrates how a reverse restore operation works:
Chapter 8. Optional feature codes for the DS8000
109