HP StorageWorks XP Remote Web Console Software - Manual (Page 22)

22 ShadowImage for the XP128/XP1024/XP10000/XP12000
Resynchronize Pair Operations (Normal, Quick, Reverse, Quick Restore)
To change the status of pairs from Split to Duplex or from Suspend to Duplex, you must resynchronize the
pairs. ShadowImage performs the following types of resync operations according to the speed and
direction of the resynchronization:
• Normal copy
• Quick resync
• Reverse copy
• Quick resync
The Resynchronize Volume Pair pane (see ” Resynchronizing ShadowImage Pairs ” on page 57) allows you
to resynchronize split and suspended ShadowImage for z/OS pairs. When the resync operation starts, the
pair status changes to resync or resync-r. When the resync is complete, the pair status changes to duplex.
Command View XP or XP Remote Web Console resumes Slz update copy operations after the pair status
changes to duplex. The S-VOL remains fully accessible during a normal or quick resync operation, but is
inaccessible to all hosts during a reverse copy or quick restore operation. This ensures that data on the
S-VOL is identical to data on the T-VOL when the reverse copy or quick restore operation completes.
NOTE: You can use ShadowImage for z/OS to perform normal and quick resync operations on split and
suspended pairs, but you can perform reverse copy operations only on split pairs.
Forward Pairresync Operation
Forward pairresync operation resynchronizes pairs by copying data on S-VOLs to T-VOLs. The following
are the types of forward pairresync operations:
• Normal. The normal resync operation (see Figure 4 ) resynchronizes the T-VOL with the S-VOL. The copy
direction for a normal resync operation is S-VOL to T-VOL. The pair status during a normal resync
operation is resync, and the S-VOL remains accessible to all hosts for both read and write operations
during a normal resync operation. The T-VOL becomes inaccessible to all hosts during a normal resync
operation.
• Quick. The quick resync operation (see Figure 4 ) speeds up the normal resync operation without
copying the S-VOL data to the T-VOL. The S-VOL and the T-VOL are resynchronized when update copy
operations are performed for duplex pairs. The pair status during a quick resync operation is resync,
and the S-VOL remains accessible to all hosts for both read and write operations. The T-VOL becomes
inaccessible to all hosts during a quick resync operation.
Figure 4 Forward pairresync operations
CAUTION: Even if the copy operation is completed without any host I/O, the data in the S-VOL and the
data in the T-VOL may not be the same. Whether the S-VOL and the T-VOL have the same data depends on
the condition of the disk array. To make the S-VOL data and the T-VOL data equal, split the pair and make
the pair status split.