Flashcopy Concept

The FlashCopy function enables you to make point-in-time, full volume copies of data, with the copies immediately available for read or write access. You can use the copy with standard backup tools that are available in your environment to create backup copies on tape.
FlashCopy creates a copy of a source volume on the target volume. This copy is called a point-in-time copy. When you initiate a FlashCopy operation, a FlashCopy relationship is created between a source volume and target volume. A FlashCopy relationship is a "mapping" of the FlashCopy source volume and a FlashCopy target volume. This mapping allows a point-in-time copy of that source volume to be copied to the associated target volume. The FlashCopy relationship exists between this volume pair from the time that you initiate a FlashCopy operation until the storage unit copies all data from the source volume to the target volume or you delete the FlashCopy relationship, if it is a persistent FlashCopy.
When the data is physically copied, a background process copies tracks from the source volume to the target volume. The amount of time that it takes to complete the background copy depends on the following criteria:
The amount of data being copied
The number of background copy processes that are occurring
The other activities that are occurring on the DS8000™
FlashCopy supports the following copy options:
Consistency groups
Creates a consistent point-in-time copy of multiple volumes, with negligible host impact. You can enable FlashCopy consistency groups from the command-line interface (DS CLI).
Change recording
Activates the change recording function on the volume pair that is participating in a FlashCopy relationship. This enables a subsequent refresh to the target volume.
Establish FlashCopy on existing Metro Mirror source
Allows you to establish a FlashCopy relationship where the target volume is also the source of an existing remote mirror and copy source volume. This enables you to create full or incremental point-in-time copies at a local site and then use remote mirroring commands to copy the data to the remote site.
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 relationshipsThe 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.
FlashCopy to Metro Mirror source volumesYou can use an existing Metro Mirror source volume as a FlashCopy target volume. This process allows you to create a point-in-time copy and then make a copy of that data at a remote site.
Multiple relationship FlashCopyThe multiple relationship FlashCopy function allows a source volume to have multiple targets simultaneously.
Persistent FlashCopyA persistent FlashCopy relationship is one that does not end when the background physical copy ends. The relationship persists until it is explicitly withdrawn.
Resynchronization of FlashCopy volume pairsFlashCopy volumes resynchronization (resync) provides the ability to update an initial point-in-time copy of a source volume.
FlashCopy SE featureThe FlashCopy SE feature allocates storage space on an "as-needed" basis by using space on a target volume only when it actually copies tracks from the source volume to the target volume.