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Forward pairre
sync operation
A forward pairr
esync operation resynchronizes pairs by copying data on P-VOLs to S-VOLs. The following
are the types o
f forward pairresync operations:
• Normal.Thisoperation(seeFigure 4) resynchronizes the S-VOL with the P-VOL. The copy
direction for a normal pairresync operation is P-VOL to S-VOL. The pair status during a normal
resync operation is COPY(RS), and the P-VOL remains accessible to all hosts for read and write
operations during a normal pairresync.
• Quick.This
operation speeds up the normal pairresync operation without copying the P-VOL
data to the S-VOL. The P-VOL and S-VOL are resynchronized when update copy operations are
performed for duplex pairs (status = PAIR). The pair status during a quick pairresync operation
is PSUS(SP) until the differential map is copied, and the P-VOL remains accessible to all hosts
for read an
d write operations. The S-VOL becomes inaccessible to all hosts during a quick
pairresync operation.
Figu
re 4 Normal and quick pairresync operations
CAUTION:
Even if a copy operation is completed without any host I/O, the data in the P-VOL and S-VOL may not
beidentical.WhethertheP-VOLandtheS-VOLhavethesamedatadependsontheconditionofthe
disk
array. To make the P-VOL and S-VOL data the same, split the pair and make the pair status PSUS.
Backward pairresync operation
A backward pairresync operation resynchronizes pairs by copying data on S-VOLs to P-VOLs. The
following are the types of backward pairresync operations:
Business Copy XP user guide
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