Hitachi ShadowImage for z/OS user guide (HIT9503-96009, January 2008)

Legend
: Time flow
: Data
Resync
S-VOL
T-VOL
Duplex
Host
S-VOL
T-VOL
Resynchronized
Write Data
A
ccess permitted
A
ccess inhibited
Host
A
ccess permitted
A
ccess inhibited
Figure 7 Forward Pairresync Operations
CAUTIO
N:
Even if
the copy operation is completed without any host I/O, the data in the S-VOL and the data in
theT-VOLmaynotbethesame.WhethertheS-VOLandtheT-VOLhavethesamedatadependson
theconditionofthestoragesystem.TomaketheS-VOLdataandtheT-VOLdataequal,splitthepair
and ma
ke the pair status
split .
Backward Pairresync Operation
Backward pairresync operation resynchronizes the pairs by copying the data of T-VOLs to S-VOLs. There
are two kinds of the backward pairresync operation; the reverse pairresync operation and the quick
restore pairresync operation.
•
Reverse: The reverse copy operation (see Figure 8 on page 33) synchronizes the S-VOL with the
T-VOL. The copy direction for a reverse copy operation is T-VOL to S-VOL. lists the operational
requirements for the reverse copy operation. The pair status during a reverse copy operation is
resync-r, and the S-VOL and T-VOL become inaccessible to all hosts for write operations during a
reverse copy operation. As soon as the reverse copy operation is complete, the S-VOL becomes
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