Remote Mirror And Copy - IBM DS8000 User Manual

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relationship is explicitly withdrawn before another FlashCopy operation can be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.
Note: Persistent FlashCopy is always required for refreshing a FlashCopy target
Resynchronization of FlashCopy volume pairs
FlashCopy volumes resynchronization (resync) provides the ability to update an
initial point-in-time copy of a source volume.
You can resync your FlashCopy volumes without having to recopy your entire
volume. This process is only possible with a persistent relationship, whereby the
storage unit continually tracks updates to the source and target volumes. With
persistent relationships, the relationship between the source and target volumes is
maintained after the background copy has completed.
This function reduces the background copy completion time because only a subset
of data is copied when either the source or target volume has changed. The target
volume becomes current with the newly established point-in-time source copy.
To enable this function of FlashCopy, the storage unit uses a feature called change
recording to monitor write operations and record changes that were made to
volumes participating in FlashCopy relationships since the initial (or last)
incremental FlashCopy was performed. After the initial copy of the source volume
to the target volume, the FlashCopy relationship between the volumes is not
automatically deleted. Rather, it remains to allow the volumes to be
resynchronized. The next time that you want to update the information on your
target volume, you can resync your target volume again.
Note: If you perform a resync operation, it is sent to any source and volume pair.

Remote mirror and copy

Remote mirror and copy is a storage server feature that constantly updates a target
copy of a volume so that it matches changes that were made to its associated
source volume.
The remote mirror and copy feature is a hardware solution that enables the
mirroring of data from one site (the local site) and its associated volumes (source
volumes) to a second storage unit at another site (the recovery or remote site) and
its volumes (target volumes).
Note: Remote mirror and copy was referred to as Peer-to-Peer Remote Copy
Remote mirror and copy differs from FlashCopy in two essential ways. First, the
source and target volumes can be on the same storage server or on separate
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DS8000 User's Guide
volume.
All source and target volume pairs will be resynchronized, not just the one
pair that you selected.
(PPRC) in earlier documentation for the IBM TotalStorage Enterprise Storage
Server. Currently, the remote mirror and copy feature name is used
generically for all methods of synchronous and asynchronous methods. In
addition, in a remote mirror and copy environment, a site where production
applications run might be referred to as the production site, local site, or Site
A. A site that has mirrored data of your local site might be referred to as a
recovery site, backup site, remote site, or Site B.