<s>
FlashCopy	B-Device
is	O
an	O
IBM	O
feature	O
supported	O
on	O
various	O
IBM	O
storage	O
devices	O
that	O
made	O
it	O
possible	O
to	O
create	O
,	O
nearly	O
instantaneously	O
,	O
</s>
<s>
point-in-time	O
snapshot	B-Application
copies	O
of	O
entire	O
logical	O
volumes	O
or	O
data	O
sets	O
.	O
</s>
<s>
The	O
first	O
implementation	O
of	O
FlashCopy	B-Device
,	O
Version	O
1	O
allowed	O
entire	O
volumes	O
to	O
be	O
instantaneously	O
“	O
copied	O
”	O
to	O
another	O
volume	O
by	O
using	O
the	O
facilities	O
of	O
the	O
newer	O
Enterprise	O
Storage	O
Subsystems	O
(	O
ESS	O
)	O
.	O
</s>
<s>
Version	O
1	O
of	O
FlashCopy	B-Device
had	O
limitations	O
however	O
.	O
</s>
<s>
Although	O
the	O
copy	O
or	O
“	O
flash	O
”	O
of	O
a	O
volume	O
occurred	O
instantaneously	O
,	O
the	O
FlashCopy	B-Device
commands	O
were	O
issued	O
sequentially	O
and	O
the	O
ESS	O
required	O
a	O
brief	O
moment	O
to	O
establish	O
the	O
new	O
pointers	O
.	O
</s>
<s>
FlashCopy	B-Device
Version	O
2	O
introduced	O
the	O
ability	O
to	O
flash	O
individual	O
data	O
sets	O
and	O
then	O
added	O
support	O
for	O
“	O
consistency	O
groups	O
”	O
.	O
</s>
<s>
FlashCopy	B-Device
consistency	O
groups	O
can	O
be	O
used	O
to	O
help	O
create	O
a	O
consistent	O
point-in-time	O
copy	O
across	O
multiple	O
volumes	O
,	O
and	O
even	O
across	O
multiple	O
ESSs	O
,	O
thus	O
managing	O
the	O
consistency	O
of	O
dependent	O
writes	O
.	O
</s>
<s>
FlashCopy	B-Device
consistency	O
groups	O
are	O
used	O
in	O
a	O
single-site	O
scenario	O
in	O
order	O
to	O
create	O
a	O
time-consistent	O
copy	O
of	O
data	O
that	O
can	O
then	O
be	O
backed-up	O
and	O
sent	O
off	O
site	O
,	O
or	O
in	O
a	O
multi-site	O
Global	B-Application
Mirror	I-Application
for	O
ESS	O
implementation	O
to	O
force	O
time	O
consistency	O
at	O
the	O
remote	O
site	O
.	O
</s>
<s>
The	O
implementation	O
of	O
consistency	O
groups	O
is	O
not	O
limited	O
to	O
FlashCopy	B-Device
.	O
</s>
<s>
Global	B-Application
Mirror	I-Application
for	O
IBM	B-Device
System	I-Device
z	I-Device
series	O
(	O
formerly	O
known	O
as	O
XRC	O
or	O
eXtended	O
Remote	O
Copy	O
)	O
also	O
creates	O
consistency	O
groups	O
to	O
asynchronously	O
mirror	O
disk	O
data	O
from	O
one	O
site	O
to	O
another	O
over	O
any	O
distance	O
.	O
</s>
