HP XP Business Copy Software - Manual (Page 20)

20 Business Copy XP (BC) for the XP128/XP1024
differential map is copied, and the P-VOL remains accessible to all hosts for read and write operations.
The S-VOL becomes inaccessible to all hosts during a quick pairresync operation.
Figure 4 Normal and quick pairresync operations
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:
• Reverse. This operation (see Figure 5) synchronizes the P-VOL with the S-VOL. The copy direction for a
reverse pairresync operation is S-VOL to P-VOL. Table 5 lists operational requirements for the reverse
pairresync operation. The pair status during a reverse resync operation is COPY(RS-R), and the P-VOL
and S-VOL become inaccessible to all hosts for write operations during a reverse pairresync operation.
When the reverse pairresync is complete, the P-VOL becomes accessible. The reverse pairresync
operation can only be performed on split pairs, not on suspended pairs. The reverse pairresync
operation cannot be performed on L2 cascade pairs.
NOTE: The P-VOL remains read-enabled during the reverse pairresync operation only to enable the
host to recognize the volume. Data on the P-VOL is not guaranteed until the reverse pairresync
operation is complete and the status changes to PAIR.
• Quick Restore. This operation (Figure 5) speeds up reverse resync by changing the volume map in the
disk array to swap the contents of the P-VOL and S-VOL without copying the S-VOL data to the P-VOL.
The P-VOL and S-VOL are resynchronized when update copy operations are performed for pairs in PAIR
status. The pair status during a quick restore operation is COPY(RS-R) until the volume map change is
complete. The P-VOL and S-VOL become inaccessible to all hosts for write operations during a quick