HP StorageWorks XP Remote Web Console Software - Manual (Page 36)

URz P-VOL SIz T-VOL URz S-VOL
SIz S-VOL
ShadowImage
for z/OS ®
Universal
Replicator
for z/OS ®
Legend:
SIz S-VOL:
SIz T-VOL:
URz P-VOL:
URz S-VOL: SIz source volume
SIz target volume
URz primary data volume
URz secondary data volume
Figure 13 Siz S-VOL Forming Pair with External T-VOL and Shared as URz S-VOL
Pair Status and Time Required for Pairresync
The pairresync operation can be performed on a split pair or a suspended pair. This section describes
the relation between the pair status and the time required for pairresync operations.
• Resync for split pair: When a normal/quick resync operation is performed on a split pair, the
XP1024/XP128/XP12000/XP10000/SVS 200 copies all differential data from the S-VOL to
the T-VOL. When a reverse copy or quick restore operation is performed on a split pair, the
XP1024/XP128/XP12000/XP10000/SVS 200 copies all differential data from the T-VOL to
the S-VOL. This ensures that the S-VOL and T-VOL are properly re-synchronized in the desired
direction, and also greatly reduces the time needed to re-synchronize the pair.
• Resync for suspended pair: When a normal/quick resync operation is performed on a suspended
pair, the XP1024/XP128/XP12000/XP10000/SVS 200 copies all data on the S-VOL to the
T-VOL, since all S-VOL tracks were flagged as differential data when the pair was suspended.
Reverse resync pair and quick restore operations cannot be performed on suspended pairs. The
normal resync operation for suspended pairs is equivalent to and takes as long as the Siz initial
copy operation. If you perform the quick pairresync operation on the suspended pairs, the update
copy operation will be performed and all data will be copied to the S-VOL. In this case, the
update copy operation will take much longer than the initial copy operation.
CAUTION:
When re-synchronizing pairs, you can select the pace for the resync operation(s): slower, medium, and
faster. The slower pace minimizes the impact of Siz operations on storage system I/O performance,
while the faster pace resynchronizes the pair(s) as quickly as possible. The quick resync option provides
the fastest normal resync operation, but it may affect the storage system I/O performance.
NOTE:
•
The CESTPAIR and PPRCOPY ESTPAIR commands allow you to re-synchronize split Siz volume
pairs. See Chapter 5 on page 99 for further information on using PPRC commands to perform
Siz operations on the storage system.
• After a Siz reverse copy or quick restore operation is performed, make sure that the pair status
changes to duplex before performing a TCz resume pair operation. If you perform the TCz resume
pair operation before the pair status changes to duplex , the command (resume pair operation)
will be rejected.
Suspend Pair Operation
The Siz suspend pair operation suspends the update copy operations to the T-VOL of the pair. A Siz
pair can be suspended by the user at any time. When a Siz pair is suspended, the storage system
stops performing update copy operations to the T-VOL, continues accepting write I/O operations to the
S-VOL, and marks the entire S-VOL track as differential data. When a resync operation is performed on
a suspended pair, the entire S-VOL is copied to the T-VOL. Reverse copy and quick restore cannot be
36 Overview of Hitachi ShadowImage for z/OS Operations