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Re-synchronizing FlashCopy volume pairs
Creating a Remote FlashCopy operation (Inband FlashCopy on the
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DS8000 User's Guide
1. FlashCopy from Volume A to Volume B
2. FlashCopy from Volume A to Volume C
3. FlashCopy from Volume A to Volume D
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relationship is explicitly withdrawn before another FlashCopy operation can be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.
Note: Persistent FlashCopy is always required for refreshing a FlashCopy target
volume.
Re-synchronizing FlashCopy volumes 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
re-synchronized. 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.
All source and target volume pairs will be re-synchronized, not just the one
pair that you selected.
Remote FlashCopy operations (Inband FlashCopy on the ESS 2105) allow you to
create a FlashCopy relationship at a target (remote) site using remote FlashCopy
commands, without having an network connection to the target site.
Remote FlashCopy commands are issued to a source volume of a remote mirror
and copy volume pair on a source (local) storage unit and sent across paths (acting
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