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new pair, all P-VOL data is copied to the S-VOL. When the split operation is complete, the pair status
changes to PSUS, and you have full read/write access to the split S-VOL (even though it is still reserved).
While the pair is split, the disk array establishes a track map for the split P-VOL and S-VOL, and
records a list of the changed tracks for both volumes. The P-VOL remains fully accessible during the
pairsplit operation, and the accessibility of the S-VOL depends on the split type (see Split type). Pairsplit
operations cannot be performed on suspended (PSUE, COPY(RS), or COPY(RS-R)) pairs.
Copy pace
When splitting pairs, you can select the pace for the pending update copy operation: Slower, Medium,
and Faster. The slower pace minimizes the impact of BC operations on disk array I/O performance,
while the fas
ter pace splits the pairs as quickly as possible.
Split type
When splitting pairs, you can select the split type: Quick Split or Steady Split.
• When you specify Quick Split, the pair status changes to PSUS(SP), and the S-VOL is available
immediately for read and write I/Os (even though it is still reserved). All P-VOL data or differential
data is copied to the S-VOL in the background.
• When you specify Steady Split, the pair status changes to COPY(SP), and all P-VOL data or
differential data is copied to the S-VOL. When the operation is complete, the pair status changes
toPSUS,andyouhavefullread/writeaccesstothesplitS-VOL(eventhoughitisstillreserved).
If you want to finish the copy operation quickly in order to access the S-VOL, take the P-VOL
offline before performing the operation.
NOTE:
Refer to the Table 7 for information about read/write operations from host servers to P-VOLS and
S-VOLS of BC pairs during a pairsplit operation.
Pairresync operations
To change the status of the pairs from PSUS to PAIR, or from PSUE to PAIR, you must resynchronize the
pairs. BC can perform the following types of pairresync operations according to the speed and direction
of the resynchronization:
• Normal Copy
• Quick Resync
• Reverse Copy
• Quick Restore
Use the Pairresync pane to resynchronize split and suspended BC pairs. When the pairresync operation
starts, the pair status changes to COPY(RS) or COPY(RS-R). When the pairresync is complete, the pair
status changes to PAIR. The local disk array resumes BC update copy operations after the pair status
changes to PAIR. The P-VOL remains fully accessible during a normal pairresync operation, but is
inaccessible to all hosts during a reverse or quick restore pairresync operation. This ensures that data
on the P-VOL is identical to data on the S-VOL when the reverse or quick restore pairresync operation
completes.
NOTE:
You can use BC to perform normal or quick pairresync operations on split and suspended pairs, but you
can perform reverse or quick restore pairresync operations only on split pairs.
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Business Copy XP (BC) for the Array