HP XP Business Copy Software - Manual (Page 25)

Business Copy XP user guide for the XP10000/XP12000 25
• Normal. This operation (see Figure 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 and write operations.
The S-VOL becomes inaccessible to all hosts during a quick pairresync operation.
Figure 4 Normal and quick pairresync operations
CAUTION: If a copy operation is completed without any host I/O, the data in the P-VOL and S-VOL may
not be the same. Whether the P-VOL and the S-VOL have the same data depends on the condition of the
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:
• 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 9 shows the requirements for reverse and quick
restore pairresync operations. If you perform these operations on pairs that do not meet the
requirements, the reverse copy or quick restore command is rejected. 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.