HP Hitachi ShadowImage for Mainframe User Guide (T5213-96032, November 2011)

Figure 9 Quick Restore Operation With or Without Swap&Freeze Option
The Quick Restore pairresync operation on a pair which status is split exchanges the data in the
S-VOL and the T-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 S-VOL and the T-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 S-VOL overwrites the T-VOL.
Host I/O Performance Option
The Host I/O Performance option is used to improve host I/O responses over SIz copying processing
time. When the Host I/O Performance option is in effect, the storage system suppresses execution
of SIz copying processing, and consequently host I/O responses improve.
When SIz copying processing is suppressed by the Host I/O Performance option, the time taken
for copying increases. Also, if ShadowImage for Mainframe pairs exist, host I/O responses might
not be improved. In this case, set the Host I/O Performance option for ShadowImage for Mainframe
as well.
Copy Threshold Option
If the load of XP storage system increases, host server I/O performance (response) may be degraded.
If ShadowImage for Mainframe performs copy operations when the load of the storage system is
ShadowImage for Mainframe Options 25