![background image](http://html1.mh-extra.com/html/ibm/totalstorage-ds8000/totalstorage-ds8000_user-manual_4109708138.webp)
between
source
volume
A
and
target
volume
B.
Data
loss
occurs
on
source
volume
A.
To
keep
applications
running,
you
can
reverse
the
FlashCopy
relationship
so
that
volume
B
is
copied
to
volume
A.
Note:
A
fast
reverse
option
that
applies
to
a
Global
Mirror
operation
allows
a
FlashCopy
relationship
to
be
reversed
without
waiting
for
the
background
copy
of
a
previous
FlashCopy
relationship
to
finish.
A
Global
Mirror
operation
is
based
on
existing
Global
Copy
and
FlashCopy
operations
at
the
target
site.
Figure
8
illustrates
how
a
reverse
restore
operation
works:
FlashCopy
to
Metro
Mirror
source
volumes
You
can
use
an
existing
Metro
Mirror
source
volume
as
a
FlashCopy
target
volume.
This
process
allows
you
to
create
a
point-in-time
copy
and
then
make
a
copy
of
that
data
at
a
remote
site.
Previously,
you
could
create
a
FlashCopy
relationship
between
two
volumes
and
then
create
a
Metro
Mirror
volume
pair
by
using
the
FlashCopy
target
volume
as
the
Metro
Mirror
source
volume.
However,
you
could
not
use
an
existing
Metro
Mirror
source
volume
as
a
FlashCopy
target
volume.
This
is
no
longer
a
restriction.
You
can
create
FlashCopy
target
volumes
that
serve
as
production
volumes
and
mirror
them
to
a
remote
site
usingMetro
Mirror.
You
can
create
a
full
volume
or
incremental
point-in-time
copy
to
an
existing
Metro
Mirror
source
volume.
The
first
time
that
you
create
a
FlashCopy
operation,
the
entire
Metro
Mirror
source
volume
has
to
be
copied
to
the
remote
site,
similar
to
a
new
pair
being
established.
Afterwards,
provided
that
you
created
the
FlashCopy
volume
pair
with
the
persistent
and
change
recording
options,
you
can
perform
a
refresh
(incremental)
of
the
FlashCopy
relationship.
The
refresh
copies
only
changes
and
sends
them
to
the
remote
site,
requiring
less
time
for
the
remote
mirror
and
copy
volumes
to
be
synchronized
again.
When
you
create
a
FlashCopy
operation
and
the
logical
copy
finishes,
the
corresponding
Metro
Mirror
volume
pairs
turn
to
duplex
pending
status
as
long
as
FlashCopy initiated from Volume A to
Volume B.
olumes.
Change recording starts
on both v
Once FlashCopy is established, the
P-i-T copy is available, and Volume A
and Volume B can start receiving updates
Background copy task copies data
from Volume A to Volume B.
Reverse restore initiated from
Volume B to Volume A:
Background copy task copies
from Volume B
and Volume A to Volume A.
updated tracks
Change recording reset to track
new changes (ready for the next
incremental FlashCopy request).
Time
volA
volB
volA
volB
volA
volB
volA
volB
1t
y
ta
x
Figure
8.
Refreshing
target
volume
—
reverse
restore
112
DS8000
User’s
Guide
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