FlashCopy® Withdraw
processing for a Preserve Mirror relationship is designed to minimize
differences between the local and remote FlashCopy targets (Local B and Remote B in Figure 1), difference that can occur, even though the PPRC
pair is full duplex at all times, because the local and remote storage
servers perform the background copy for their respective relationships
in a different manner or at a different pace. Note that even without
PPRC, the content of target tracks is undetermined after a FlashCopy Withdraw.
For a FlashCopy Preserve
Mirror relationship:
- The FCWITHDR command and the FCWITHDRAW request withdraw
the mirrored relationship immediately at both the local and the remote
storage servers, unless you specify the DDSW option. An indicator
that the target PPRC pair was the target of a withdrawn preserve mirror
relationship is set, so that this can be reflected in the results
of a CQUERY command. A FlashCopy Withdraw
issued without that option to the local FlashCopy source or target (Local A or Local B)
starts a background copy for both the local and remote relationships.
- The DDSW option, when used with a FlashCopy Withdraw issued to the remote FlashCopy source (Remote A),
starts a background copy for the remote relationship. A FlashCopy Withdraw with DDSW
issued to the remote FlashCopy target
(Remote B) will be rejected.
- The FCWITHDR command and the FCWITHDRAW request issued
to either the remote FlashCopy source
or target (Remote A or Remote B) withdraw only the remote relationship,
and set an indicator that there may be tracks that are not identical
only on the remote device.