Manual

Pair resynchronization
You resynchronize a pair that is split or suspended by the system. Resynchronizing updates the
S-VOL so that it is again paired with the P-VOL.
CAUTION: Resynchronizing the pair does not guarantee that P-VOL data is the same as S-VOL
data. Data in the two volumes is the same only if the P-VOL is offline and the pair has been split
and is in Split/SUSPOP status.
Related information
• “Types of resync operations” (page 45)
• “Prerequisite information for resynchronizing” (page 46)
• “Resynchronizing pairs” (page 46)
Types of resync operations
You can resynchronize pairs from P-VOL to S-VOL and from S-VOL to P-VOL. The types of resync
operation follow, with requirements and restrictions:
• Normal Copy. Forward full resync, from P-VOL to S-VOL.
The P-VOL is accessible to hosts for both read and write operations.◦
◦ The S-VOL is inaccessible to hosts.
• Quick Resync. Forward resync from P-VOL to S-VOL but does not data copy. The status changes
to DUPLEX but does not resynchronize the data to the S-VOL.
◦ Differential data is copied to the S-VOL during update copying.
◦ The P-VOL is accessible to hosts for read and write operations. The S-VOL is inaccessible
to all hosts.
◦ Data in the P-VOL and S-VOL may not be the same after a Quick Resync even when there
a host I/O is not present during the operation. Split the pair to ensure that data is the
same.
• Reverse Copy. Reverse full resync from S-VOL to P-VOL.
The P-VOL is inaccessible to hosts.◦
◦ All differential data is updated to the P-VOL.
◦ Pairs sharing the same P-VOL must be in Split/SUSPOP or Suspend/SUSPER status.
◦ If the pair shares a volume with Cnt Ac-S Z or Cnt Ac-J Z, you must suspend the Cnt Ac-S
Z or Cnt Ac-J Z pair to perform the Reverse Copy or Quick Restore operation.
◦ You cannot create a Cnt Ac-S Z or Cnt Ac-J Z pair with a volume shared by BC Z during
the Reverse Copy or Quick Restore operation.
◦ When the Reverse Copy or Quick Restore is in progress, you cannot create, split, or
resync any pair sharing the same P-VOL. However, the pairs can be deleted or suspended.
◦ Reverse Copy cannot be used for the following:
- BC L2 pair
Pair resynchronization 45