<s>
Oracle	B-Operating_System
Clusterware	I-Operating_System
is	O
the	O
cross-platform	B-Operating_System
cluster	B-Architecture
software	O
required	O
to	O
run	O
the	O
Real	B-Operating_System
Application	I-Operating_System
Clusters	I-Operating_System
(	O
RAC	O
)	O
option	O
for	O
Oracle	B-General_Concept
Database	I-General_Concept
.	O
</s>
<s>
It	O
provides	O
the	O
basic	O
clustering	O
services	O
at	O
the	O
operating-system	B-General_Concept
level	O
that	O
enable	O
Oracle	B-General_Concept
Database	I-General_Concept
software	O
to	O
run	O
in	O
clustering	O
mode	O
.	O
</s>
<s>
In	O
earlier	O
versions	O
of	O
Oracle	B-General_Concept
(	O
release	O
9i	O
and	O
earlier	O
)	O
,	O
RAC	O
required	O
a	O
vendor-supplied	O
clusterware	B-Operating_System
like	O
Sun	B-Operating_System
Cluster	I-Operating_System
or	O
Veritas	B-Operating_System
Cluster	I-Operating_System
Server	I-Operating_System
(	O
except	O
when	O
running	O
on	O
Linux	B-Application
or	O
on	O
Microsoft	B-Application
Windows	I-Application
)	O
.	O
</s>
<s>
Oracle	B-Operating_System
Clusterware	I-Operating_System
is	O
the	O
software	O
which	O
enables	O
the	O
nodes	O
to	O
communicate	O
with	O
each	O
other	O
,	O
allowing	O
them	O
to	O
form	O
the	O
cluster	B-Architecture
of	O
nodes	O
which	O
behaves	O
as	O
a	O
single	O
logical	O
server	O
.	O
</s>
<s>
Oracle	B-Operating_System
Clusterware	I-Operating_System
is	O
run	O
by	O
Cluster	B-Architecture
Ready	O
Services	O
(	O
CRS	O
)	O
consisting	O
of	O
two	O
key	O
components	O
:	O
Oracle	B-General_Concept
Cluster	B-Architecture
Registry	O
(	O
OCR	O
)	O
,	O
which	O
records	O
and	O
maintains	O
the	O
cluster	B-Architecture
and	O
node	O
membership	O
information	O
;	O
voting	O
disk	O
,	O
which	O
polls	O
for	O
consistent	O
heartbeat	O
information	O
from	O
all	O
the	O
nodes	O
when	O
the	O
cluster	B-Architecture
is	O
running	O
,	O
and	O
acts	O
as	O
a	O
tiebreaker	O
during	O
communication	O
failures	O
.	O
</s>
<s>
The	O
CRS	O
service	O
has	O
four	O
components	O
,	O
each	O
handling	O
a	O
variety	O
of	O
functions	O
:	O
Cluster	B-Architecture
Ready	O
Services	O
daemon	O
(	O
CRSd	O
)	O
,	O
Oracle	B-General_Concept
Cluster	B-Architecture
Synchronization	O
Service	O
Daemon	O
(	O
OCSSd	O
)	O
,	O
Event	O
Volume	O
Manager	O
Daemon	O
(	O
EVMd	O
)	O
,	O
and	O
Oracle	B-General_Concept
Process	O
Clusterware	B-Operating_System
Daemon	O
(	O
OPROCd	O
)	O
.	O
</s>
<s>
Failure	O
or	O
death	O
of	O
the	O
CRS	O
daemon	O
can	O
cause	O
node	O
failure	O
,	O
which	O
triggers	O
automatic	O
reboots	O
of	O
the	O
nodes	O
to	O
avoid	O
the	O
corruption	O
of	O
data	O
(	O
due	O
to	O
the	O
possible	O
failure	O
of	O
communication	O
between	O
the	O
nodes	O
)	O
,	O
also	O
known	O
as	O
fencing	B-Operating_System
.	O
</s>
<s>
The	O
CRS	O
daemon	O
runs	O
as	O
"	O
root	O
"	O
(	O
super	B-Application
user	I-Application
)	O
on	O
UNIX	B-Application
platforms	O
and	O
runs	O
as	O
a	O
service	O
on	O
Windows	O
platforms	O
.	O
</s>
<s>
The	O
following	O
functions	O
are	O
provided	O
by	O
the	O
Oracle	B-General_Concept
Cluster	B-Architecture
Ready	O
Services	O
daemon	O
(	O
CRSd	O
)	O
:	O
</s>
<s>
During	O
planned	O
clusterware	B-Operating_System
start	O
it	O
is	O
started	O
as	O
‘	O
reboot’	O
mode	O
.	O
</s>
<s>
Runs	O
as	O
‘	O
root’	O
on	O
Unix	B-Application
and	O
‘	O
LocalSystem’	O
on	O
windows	O
and	O
automatically	O
restarts	O
in	O
case	O
of	O
failure	O
.	O
</s>
<s>
CRS	O
requires	O
the	O
public	O
interface	O
,	O
private	O
interface	O
and	O
the	O
Virtual	B-Operating_System
IP	I-Operating_System
(	O
VIP	O
)	O
for	O
the	O
operation	O
.	O
</s>
<s>
Oracle	B-General_Concept
Cluster	B-Architecture
Synchronization	O
Services	O
daemon	O
(	O
OCSSd	O
)	O
provides	O
basic	O
‘	O
group	O
services’	O
support	O
.	O
</s>
<s>
As	O
such	O
,	O
it	O
provides	O
synchronization	O
services	O
between	O
nodes	O
,	O
access	O
to	O
the	O
node	O
membership	O
information	O
,	O
as	O
well	O
as	O
enabling	O
basic	O
cluster	B-Architecture
services	O
,	O
including	O
cluster	B-Architecture
group	O
services	O
and	O
cluster	B-Architecture
locking	O
.	O
</s>
<s>
It	O
can	O
also	O
run	O
without	O
integration	O
with	O
vendor	O
clusterware	B-Operating_System
.	O
</s>
<s>
This	O
is	O
also	O
required	O
in	O
a	O
single	O
instance	O
configuration	O
if	O
Automatic	B-Application
Storage	I-Application
Management	I-Application
(	O
ASM	O
)	O
is	O
used	O
.	O
</s>
<s>
ASM	O
was	O
a	O
new	O
feature	O
in	O
Oracle	B-General_Concept
10g	I-General_Concept
.	O
</s>
<s>
OCSSd	O
runs	O
as	O
the	O
"	O
oracle	B-General_Concept
"	O
user	O
.	O
</s>
<s>
The	O
following	O
functions	O
are	O
provided	O
by	O
the	O
Oracle	B-General_Concept
Cluster	B-Architecture
Synchronization	O
Services	O
daemon	O
(	O
OCSSd	O
)	O
:	O
</s>
<s>
EVMd	O
runs	O
as	O
the	O
"	O
oracle	B-General_Concept
"	O
user	O
.	O
</s>
<s>
OPROCd	O
provides	O
the	O
server	O
fencing	B-Operating_System
solution	O
for	O
the	O
Oracle	B-Operating_System
Clusterware	I-Operating_System
.	O
</s>
<s>
It	O
is	O
the	O
process	O
monitor	O
for	O
Oracle	B-Operating_System
Clusterware	I-Operating_System
and	O
it	O
uses	O
the	O
hang	O
check	O
timer	O
or	O
watchdog	B-Application
timer	I-Application
(	O
depending	O
on	O
the	O
implementation	O
)	O
for	O
the	O
cluster	B-Architecture
integrity	O
.	O
</s>
<s>
OPROCd	O
is	O
locked	O
in	O
the	O
memory	O
and	O
runs	O
as	O
a	O
real	B-General_Concept
time	I-General_Concept
process	I-General_Concept
.	O
</s>
<s>
OPROCd	O
is	O
so	O
important	O
that	O
even	O
it	O
is	O
being	O
monitored	O
by	O
a	O
process	O
called	O
OCLSOMON	O
and	O
causes	O
a	O
cluster	B-Architecture
node	O
to	O
reboot	O
if	O
OPROCd	O
is	O
hung	O
.	O
</s>
