HP XP Business Copy Software - Manual (Page 24)

Figure 9 (page 24) shows the state of the S-VOL after the quick restore operation with or without
the Swap&Freeze option.
Figure 9 Quick Restore Operation With or Without Swap&Freeze Option
The Quick Restore pairresync operation on a pair with status PSUS exchanges the data in the
P-VOL and the S-VOL of the pair. If you use Swap&Freeze option when performing the Quick
Restore pairresync operation, the update copy operation will not take place after the Quick Restore
pairresync operation is complete. Therefore, the data of the P-VOL and the S-VOL is kept exchanged.
If you do not use Swap&Freeze option when performing the Quick Restore pairresync operation,
the update copy operation will take place after the Quick Restore pairresync operation is complete,
and the data in the P-VOL overwrites the S-VOL.
Host I/O Performance Option
The Host I/O Performance option improves host I/O responses over XP Business Copy copying
processing time. When the Host I/O Performance option is used, the storage system suppresses
the execution of XP Business Copy copying processing, and consequently the host I/O responses
improve.
When XP Business Copy copy processing is suppressed by the Host I/O Performance option, the
time taken for copying increases. Also, if XP Business Copy™ for Mainframe pairs exist, host I/O
responses might not be faster. In this case, set the Host I/O Performance option for ShadowImage
for Mainframe as well.
Copy Threshold Option
If the load of the storage system increases, the host server I/O performance (response) may be
degraded. If XP Business Copy performs copy operations when the load of the storage system is
heavy, it is more likely that host server I/O performance (response) may be degraded. The Copy
Threshold option temporarily stops the copy operations when the load of the storage system is
heavy. If you set this option, you can minimize the degradation of host I/O performance by
temporarily stopping XP Business Copy copy operations when the storage system load is heavy.
XP Business Copy has another option called the Host I/O Performance option, which maintains
host I/O performance (response). The Host I/O Performance option suppresses the copy operations
regardless of the status of the storage system. However, the Copy Threshold option is effective only
24 About XP Business Copy Operations