HP P9000 Business Copy for Mainframe Systems User Guide (AV400-96386, October 2011)

Resynchronize pairs
You resynchronize a pair that was split by a user or suspended by the system. Resynchronizing
updates the T-VOL so that it is again paired with the S-VOL.
CAUTION: Resynchronizing the pair does not guarantee that S-VOL data is the same as T-VOL
data. To make the S-VOL data and the T-VOL data equal, split the pair and make the pair status
Split.
• You can forward resync—from S-VOL to T-VOL, and reverse resync—from T-VOL to S-VOL.
You can perform a Normal Copy or a Quick Resync, in both directions.◦
◦ The S-VOL remains accessible to hosts for both read and write operations during a Normal
Copy operation. The T-VOL becomes inaccessible to hosts during a Normal Copy
operation.
◦ The S-VOL remains read-disabled during the Reverse Copy operation.
• In a forward Quick Resync from S-VOL to T-VOL, status changes to Duplex without actually
resynchronizing the data in the T-VOL. Differential data is copied to the T-VOL when update
copy operations are performed.
◦ The S-VOL remains accessible to all hosts for both read and write operations during a
quick resync operation. The T-VOL becomes inaccessible to all hosts during a Normal
Copy operation.
◦ In a forward Quick Resync you cannot be sure the data in the S-VOL and T-VOL is the
same when there is no host I/O during the operation. You must split the pair to ensure
that data is the same.
• In a reverse Quick Resync (called Quick Restore), the S-VOL and T-VOL are swapped. No
actual data is copied, and the pair is placed in Duplex status.
◦ The S-VOL and T-VOL are inaccessible during this operation. As soon as the Reverse
Copy operation is complete, the S-VOL becomes accessible.
◦ When differential data between S-VOL and T-VOL is small, the Reverse Copy operation
may be completed faster than the Quick Restore operation.
• If you perform maintenance with SVP or Remote Web Console during the Quick Restore
operation, the processing time of this operation may take longer. If you must complete the
Quick Restore operation within a given length of time, do not perform maintenance during
the Quick Restore operation.
CAUTION: If you change the mode of SVP to the Modify mode during the Quick Restore
operation or perform the Quick Restore operation when SVP is in the Modify mode, the status
of the Business Copy Z pair may be held in Resync-R. And also, during the configuration with
Remote Web Console or the tasks of Remote Web Console being remaining, the status of the
Business Copy Z pair may be held in Resync-R. When you resume the Quick Restore operation,
stop the configuration and tasks with Remote Web Console.
Prerequisite information
• With the Reverse Copy or Quick Restore operation, the pair must be in Split status.
• The pairresync normally takes less time when the pair is in Split status than for Suspend status.
This is because the amount of differential data accumulated for a split pair is usually far less
than the total amount of S-VOL, which must be copied in full if the pair is suspended by the
system.
HP Confidential Resynchronize pairs 37