HP XP Business Copy Software - Manual (Page 24)

24 Business Copy XP (BC) for the XP10000/XP12000
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 8 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.
Forward pairresync operation
A forward pairresync operation resynchronizes pairs by copying data on P-VOLs to S-VOLs. The following
are the types of forward pairresync operations:
Table 8 Read/write operations during pairsplit operations
Operations Volumes Quick Split Steady Split
Read P-VOL All data can be read
S-VOL The areas that are already copied can be
read.
If the host server tries to read data that is
not yet copied, Business Copy XP copies
that data from the P-VOL, and the host
server can read the data when the copy
is complete.
Cannot be read, although read
processing finishes normally.
Write P-VOL Write operations for the area that is already copied to the S-VOL are performed
normally.
If the host server tries to write data to an area that is not copied yet, the new data
will be written after the original P-VOL data is copied to the S-VOL.
S-VOL The areas that are already copied can be
written to.
If the host server tries to write data to an
area that is not copied yet, Business
Copy XP copies that area from the P-VOL,
and the host server can write data to the
area after the copy operation completes.
Data cannot be written, and write
processing finishes abnormally.