IBM System storage DS6000 Series, Redbook

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Chapter 27. Combining Copy Service functions
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consistent with the secondary. The local during this process is still being updated and is
changing. The remote will have a snapshot of the time since the freeze was issued.
Figure 27-2 Global Copy changed to Metro Mirror and direction reversed
Once data migration and consistency have been accomplished at the remote site, you can
start production at the remote site, if desired. In this case all applications must first be
stopped at the local site and the direction of the mirror is reversed so that Metro Mirror is now
running from the remote to the tertiary site, and Global Copy is running from the tertiary site to
the secondary site and then to the primary site. Figure 27-2 shows the new configuration with
the Metro Mirror and Global Copy reversed and production running at the remote site.
In this example, it is shown that to protect the production at the remote, the remote copy
relations can be reversed to use the tertiary, secondary, or local volumes as targets. These
copy relations would be created before starting production at the remote site. Since the
relationships from the secondary to the tertiary and from the tertiary to the remote are both in
a cascaded relationship, to reverse the directions Global Copy must first be removed and
then recreated in the reverse directions.
Note: No I/O should be running at any time at any of the sites while the reversal of the
remote copy relations is being done. This would corrupt the resulting data, and
consequently require a full copy.
A
A
B
B
DS6K DS6K
PPRC-- GC
DWDM DWDM
<50 Kms
C
C
D
D
DS6K DS6K
PPRC-- MM PPRC-- GC PPRC-- GC
Local
Secondary
Tertiary
Remote