Hitachi ShadowImage for z/OS user guide (HIT9503-96009, January 2008)

Re-synchroniz

e Pair Operations (Normal, Quick, Reverse, Quick Restore)

To change the status of the pairs from Split to Duplex, or from Suspend to Duplex, you must re-synchronize

the pairs. Siz allows you to perform four different types of resync operations according to the speed

and direction of the resynchronization:

•

Normal Copy (see section Forward Pairresync Operation,page30)

•

Quick Resync

(see section Forward Pairresync Operation, page 30)

•

ReverseCopy(seesection“Backward Pairresync Operation”onpage31)

The Re-synch

ronize Volume Pair dialog box (see section

“Re-synchr

onizing Hitachi ShadowImage for z/OS Pairs” on page 83) allows

you to re-synchronize split and suspended Siz 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.The

storage system resumes Siz update copy operations after the pair status changes to duplex.TheS-VOL

remains fully accessible during a normal/quick resync operation, but becomes inaccessible to all hosts

during a re

verse copy or quick restore operation. This ensures that the data on the S-VOL is identical to

the data on the T-VOL when the reverse copy or quick restore operation completes.

NOTE:

Siz allows you to perform normal/quick resync operations on split and suspended pairs, but reverse copy

operatio

ns can only be performed on split pairs.

Forward Pairresync Operation

Forward pairresync operation resynchronizes the pairs by copying the data of S-VOLs to T-VOLs. There

are two kinds of the forward pairresync operation, the normal pairresync operation and quick pairresync

operation.

•

Normal: The normal resync operation (see Figure 7, page 31) 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,andtheS-VOLremainsaccessibletoallhostsforbothread

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 pair operation (see Figure 7, page 31) speeds up the normal resync pair

operation by not copying the S-VOL data to the T-VOL right away. Instead, the T-VOL is gradually

re-synchronized with the S-VOL as host updates are performed, when update copy is scheduled

(XP1024/XP128/XP12000/XP10000/SVS 200 internal), or when a user issues another split

pair command for the pair. The S-VOL remains accessible to all hosts for both read and write

operations during a quick resync pair (same as normal resync pair). The T-VOL becomes

inaccessible to all hosts during a quick resync pair operation (same as normal resync pair).

Overview of Hitachi ShadowImage for z/OS Operations