FlashCopy is an optional function.
The FlashCopy function 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 the volume pair in either case:
v
From the time that you initiate a FlashCopy operation until the storage system
copies all data from the source volume to the target volume.
v
Until you explicitly delete the FlashCopy relationship if it was created as a
persistent FlashCopy relationship.
One of the main benefits of the FlashCopy function is that the point-in-time copy is
immediately available for creating a backup of production data. The target volume
is available for read and write processing so it can be used for testing or backup
purposes. Data is physically copied from the source volume to the target volume
by using a background process. (A FlashCopy operation without a background
copy is also possible, which allows only data modified on the source to be copied
to the target volume.) The amount of time that it takes to complete the background
copy depends on the following criteria:
v
The amount of data to be copied
v
The number of background copy processes that are occurring
v
The other activities that are occurring on the storage systems
The FlashCopy function 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 DS CLI.
Change recording
Activates the change recording function on the volume pair that is
participating in a FlashCopy relationship. This function enables a
subsequent refresh to the target volume.
Establish FlashCopy on existing Metro Mirror source
Establish a FlashCopy relationship, where the target volume is also the
source of an existing remote mirror and copy source volume. This allows
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 Incremental FlashCopy
Allows a source volume to establish incremental flash copies to a
maximum of 12 targets.
Chapter 3. Data management features
47
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