<s>
Automatic	B-Application
Storage	I-Application
Management	I-Application
(	O
ASM	O
)	O
is	O
a	O
feature	O
provided	O
by	O
Oracle	B-Application
Corporation	I-Application
within	O
the	O
Oracle	B-General_Concept
Database	I-General_Concept
from	O
release	O
Oracle	B-General_Concept
10g	I-General_Concept
(	O
revision	O
1	O
)	O
onwards	O
.	O
</s>
<s>
To	O
do	O
so	O
,	O
it	O
provides	O
tools	O
to	O
manage	O
file	B-Application
systems	I-Application
and	O
volumes	O
directly	O
inside	O
the	O
database	O
,	O
allowing	O
database	B-General_Concept
administrators	I-General_Concept
(	O
DBAs	O
)	O
to	O
control	O
volumes	O
and	O
disks	O
with	O
familiar	O
SQL	B-Language
statements	O
in	O
standard	O
Oracle	B-General_Concept
environments	O
.	O
</s>
<s>
Thus	O
DBAs	O
do	O
not	O
need	O
extra	O
skills	O
in	O
specific	O
file	B-Application
systems	I-Application
or	O
volume	B-Application
managers	I-Application
(	O
which	O
usually	O
operate	O
at	O
the	O
level	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
)	O
.	O
</s>
<s>
ASM	O
creates	O
extents	B-Application
out	O
of	O
datafiles	O
,	O
log-files	O
,	O
system	O
files	O
,	O
control	O
files	O
and	O
other	O
database	O
structures	O
.	O
</s>
<s>
The	O
system	O
then	O
spreads	O
these	O
extents	B-Application
across	O
all	O
disks	O
in	O
a	O
"	O
diskgroup	O
"	O
.	O
</s>
<s>
One	O
can	O
think	O
of	O
a	O
diskgroup	O
in	O
ASM	O
as	O
a	O
Logical	B-Application
Volume	I-Application
Manager	I-Application
volume	B-Application
group	I-Application
—	O
with	O
an	O
ASM	O
file	O
corresponding	O
to	O
a	O
logical	B-Application
volume	I-Application
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
existing	O
Oracle	B-General_Concept
background	B-Operating_System
processes	I-Operating_System
,	O
ASM	O
introduces	O
two	O
new	O
ones	O
-	O
OSMB	O
and	O
RBAL	O
.	O
</s>
<s>
Automatic	B-Application
Storage	I-Application
Management	I-Application
(	O
ASM	O
)	O
simplifies	O
administration	O
of	O
Oracle-related	O
files	O
by	O
allowing	O
the	O
administrator	O
to	O
reference	O
disk	O
groups	O
(	O
rather	O
than	O
individual	O
disks	O
and	O
files	O
)	O
which	O
ASM	O
manages	O
.	O
</s>
<s>
that	O
also	O
includes	O
striping	B-General_Concept
and	O
mirroring	B-General_Concept
to	O
provide	O
balanced	O
and	O
secure	O
storage	O
.	O
</s>
<s>
DBAs	O
can	O
use	O
the	O
ASM	O
functionality	O
in	O
combination	O
with	O
existing	O
raw	O
and	O
cooked	O
file-systems	B-Application
,	O
along	O
with	O
OMF	O
and	O
manually	O
managed	O
files	O
.	O
</s>
<s>
The	O
level	O
of	O
redundancy	O
and	O
the	O
granularity	O
of	O
the	O
striping	B-General_Concept
can	O
be	O
controlled	O
using	O
templates	O
.	O
</s>
<s>
Oracle	B-Application
Corporation	I-Application
provides	O
default	O
templates	O
for	O
each	O
file-type	O
stored	O
by	O
ASM	O
,	O
but	O
additional	O
templates	O
can	O
be	O
defined	O
as	O
needed	O
.	O
</s>
<s>
For	O
two-way	O
mirroring	B-General_Concept
,	O
a	O
disk	O
group	O
might	O
contain	O
two	O
failure	O
groups	O
,	O
in	O
which	O
case	O
individual	O
files	O
are	O
written	O
to	O
two	O
locations	O
.	O
</s>
<s>
Oracle	B-Application
ASM	I-Application
Dynamic	O
Volume	B-Application
Manager	I-Application
provides	O
the	O
foundation	O
for	O
the	O
ASM	O
Cluster	O
File	B-Application
System	I-Application
(	O
ACFS	O
)	O
.	O
</s>
<s>
One	O
can	O
configure	O
ASM	O
diskgroups	O
to	O
have	O
no	O
redundancy	O
(	O
external	O
)	O
,	O
two-way	O
mirroring	B-General_Concept
(	O
normal	O
)	O
,	O
or	O
three-way	O
mirroring	B-General_Concept
(	O
high	O
)	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
external	O
redundancy	O
,	O
ASM	O
does	O
not	O
do	O
any	O
software	O
mirroring	B-General_Concept
,	O
but	O
only	O
stripes	O
its	O
files	O
across	O
all	O
the	O
disks	O
that	O
belong	O
to	O
the	O
disk	O
group	O
that	O
does	O
external	O
redundancy	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
normal	O
redundancy	O
,	O
ASM	O
does	O
two-way	O
mirroring	B-General_Concept
,	O
meaning	O
that	O
ASM	O
maintains	O
two	O
copies	O
of	O
the	O
data	O
through	O
software	O
mirroring	B-General_Concept
.	O
</s>
<s>
In	O
the	O
case	O
of	O
high	O
redundancy	O
,	O
ASM	O
does	O
three-way	O
mirroring	B-General_Concept
,	O
maintaining	O
three	O
copies	O
of	O
the	O
data	O
through	O
software	O
mirroring	B-General_Concept
.	O
</s>
