<s>
Switchover	B-General_Concept
is	O
the	O
manual	O
switch	O
from	O
one	O
system	O
to	O
a	O
redundant	O
or	O
standby	O
computer	B-Application
server	I-Application
,	O
system	O
,	O
or	O
network	B-Architecture
upon	O
the	O
failure	O
or	O
abnormal	B-Application
termination	I-Application
of	O
the	O
previously	O
active	O
server	B-Application
,	O
system	O
,	O
or	O
network	B-Architecture
,	O
or	O
to	O
perform	O
system	O
maintenance	O
,	O
such	O
as	O
installing	O
patches	O
,	O
and	O
upgrading	O
software	O
or	O
hardware	O
.	O
</s>
<s>
Automatic	O
switchover	B-General_Concept
of	O
a	O
redundant	O
system	O
on	O
an	O
error	O
condition	O
,	O
without	O
human	O
intervention	O
,	O
is	O
called	O
failover	B-General_Concept
.	O
</s>
<s>
Manual	O
switchover	B-General_Concept
on	O
error	O
would	O
be	O
used	O
if	O
automatic	O
failover	B-General_Concept
is	O
not	O
available	O
,	O
possibly	O
because	O
the	O
overall	O
system	O
is	O
too	O
complex	O
.	O
</s>
