
The
use
of
the
persistent
FlashCopy
function
requires
that
the
FlashCopy
relationship
is
explicitly
withdrawn
before
another
FlashCopy
operation
can
be
performed.
While
this
restriction
does
not
guarantee
that
a
point-in-time
copy
cannot
be
overwritten
by
mistake,
it
does
provide
an
extra
measure
of
security.
Note:
Persistent
FlashCopy
is
always
required
for
refreshing
a
FlashCopy
target
volume.
Resynchronization
of
FlashCopy
volume
pairs
FlashCopy
volumes
resynchronization
(resync)
provides
the
ability
to
update
an
initial
point-in-time
copy
of
a
source
volume.
You
can
resync
your
FlashCopy
volumes
without
having
to
recopy
your
entire
volume.
This
process
is
only
possible
with
a
persistent
relationship,
whereby
the
storage
unit
continually
tracks
updates
to
the
source
and
target
volumes.
With
persistent
relationships,
the
relationship
between
the
source
and
target
volumes
is
maintained
after
the
background
copy
has
completed.
This
function
reduces
the
background
copy
completion
time
because
only
a
subset
of
data
is
copied
when
either
the
source
or
target
volume
has
changed.
The
target
volume
becomes
current
with
the
newly
established
point-in-time
source
copy.
To
enable
this
function
of
FlashCopy,
the
storage
unit
uses
a
feature
called
change
recording
to
monitor
write
operations
and
record
changes
that
were
made
to
volumes
participating
in
FlashCopy
relationships
since
the
initial
(or
last)
incremental
FlashCopy
was
performed.
After
the
initial
copy
of
the
source
volume
to
the
target
volume,
the
FlashCopy
relationship
between
the
volumes
is
not
automatically
deleted.
Rather,
it
remains
to
allow
the
volumes
to
be
resynchronized.
The
next
time
that
you
want
to
update
the
information
on
your
target
volume,
you
can
resync
your
target
volume
again.
Note:
If
you
perform
a
resync
operation,
it
is
sent
to
any
source
and
volume
pair.
All
source
and
target
volume
pairs
will
be
resynchronized,
not
just
the
one
pair
that
you
selected.
Remote
mirror
and
copy
Remote
mirror
and
copy
is
a
storage
server
feature
that
constantly
updates
a
target
copy
of
a
volume
so
that
it
matches
changes
that
were
made
to
its
associated
source
volume.
The
remote
mirror
and
copy
feature
is
a
hardware
solution
that
enables
the
mirroring
of
data
from
one
site
(the
local
site)
and
its
associated
volumes
(source
volumes)
to
a
second
storage
unit
at
another
site
(the
recovery
or
remote
site)
and
its
volumes
(target
volumes).
Note:
Remote
mirror
and
copy
was
referred
to
as
Peer-to-Peer
Remote
Copy
(PPRC)
in
earlier
documentation
for
the
IBM
TotalStorage
Enterprise
Storage
Server.
Currently,
the
remote
mirror
and
copy
feature
name
is
used
generically
for
all
methods
of
synchronous
and
asynchronous
methods.
In
addition,
in
a
remote
mirror
and
copy
environment,
a
site
where
production
applications
run
might
be
referred
to
as
the
production
site,
local
site,
or
Site
A.
A
site
that
has
mirrored
data
of
your
local
site
might
be
referred
to
as
a
recovery
site,
backup
site,
remote
site,
or
Site
B.
Remote
mirror
and
copy
differs
from
FlashCopy
in
two
essential
ways.
First,
the
source
and
target
volumes
can
be
on
the
same
storage
server
or
on
separate
112
DS8000
User’s
Guide
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