IBM System storage DS6000 Series, Redbook

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Chapter 23. Global Mirror options and configuration
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Example 23-8 Withdraw Global Mirror FlashCopy relationship with ACTION(COMMIT)
//* -------------------------------------------------------------- ***
//FCWITHDR EXEC PGM=IKJEFT01
//SYSPRINT DD SYSOUT=*
//SYSTSPRT DD SYSOUT=*
//SYSTSIN DD DDNAME=SYSIN
FCWITHDR SDEVN(X'6400' TDEVN(X'6500') ACTION(COMMIT)
23.7.5 Set consistent data on B volumes
At this point only the C volumes comprise a set of consistent data volumes. The B volumes
per definition do not provide consistent data, because Global Copy does not provide data
consistency.
Figure 23-14 Set a consistent set of B volumes using the C volumes as source
We want to have two good copies of the data at the recovery site. The aim is to have a
consistent set of volumes to work with, still keeping a good copy to which we can resort if
needed. The next step is then to create the same consistency on the B volumes as we have
on the C volumes; see Figure 23-14. This can be achieved with the FlashCopy parameter
ACTION(FRR) in the FlashCopy establish command (FRR stands for
fast reverse restore)
.
The DS CLI also provides this option with the reverseflash command, with the parameter
-fast .
The command with fast reverse restore is aimed to the FlashCopy target volume (C) as the
new FlashCopy source; see Figure 23-14.
Fast reverse restore (FRR) implies the following FlashCopy attributes:
򐂰 Start background copy from C to B.
򐂰 No change recording.
򐂰 Target volume may be a Global Copy primary, which in this case is the suspended Global
Copy primary volume. This is needed because when we previously executed the Failover
function, we changed the Global Copy secondary from pending to primary suspended.
򐂰 Not persistent, which ends this FlashCopy relationship once the background copy
completes. This allows you to check that all FRR operations completed before moving on
to the next step.
Primary
Primary
A
Primary
Primary
A
Tertiary
C
Primary
Primary
A
Primary
Primary
A
B
Host
Remote site
Primary
Primary
A
Primary
Primary
A
Primary
A
PENDING
Primary
SUSPENDED
FRR FlashCopy
Local site