HP XP P9500 User Manual page 9

Figure 4 Update copy operation
Although an initial copy completes and pair status changes to PAIR, the data in the P-VOL and
S-VOL may not be the same because the copy of the update data is performed asynchronously.
To ensure that P-VOL and S-VOL data are the same at a certain point in time, the pair must be split.
CAUTION: If the copy operation is completed without any host I/O, the data in the P-VOL and
the data in the S-VOL may not be the same. To make the P-VOL data and the S-VOL data equal,
split the pair and make the pair status PSUS.
Initial and update copy operations 9