<s>
Shortest	B-Operating_System
job	I-Operating_System
next	I-Operating_System
(	O
SJN	O
)	O
,	O
also	O
known	O
as	O
shortest	B-Operating_System
job	I-Operating_System
first	I-Operating_System
(	O
SJF	O
)	O
or	O
shortest	O
process	B-Operating_System
next	O
(	O
SPN	O
)	O
,	O
is	O
a	O
scheduling	O
policy	O
that	O
selects	O
for	O
execution	O
the	O
waiting	O
process	B-Operating_System
with	O
the	O
smallest	O
execution	O
time	O
.	O
</s>
<s>
SJN	O
is	O
a	O
non-preemptive	O
algorithm	O
.	O
</s>
<s>
Shortest	B-Operating_System
remaining	I-Operating_System
time	I-Operating_System
is	O
a	O
preemptive	B-Operating_System
variant	O
of	O
SJN	O
.	O
</s>
<s>
Shortest	B-Operating_System
job	I-Operating_System
next	I-Operating_System
is	O
advantageous	O
because	O
of	O
its	O
simplicity	O
and	O
because	O
it	O
minimizes	O
the	O
average	O
amount	O
of	O
time	O
each	O
process	B-Operating_System
has	O
to	O
wait	O
until	O
its	O
execution	O
is	O
complete	O
.	O
</s>
<s>
However	O
,	O
it	O
has	O
the	O
potential	O
for	O
process	B-Operating_System
starvation	I-Operating_System
for	O
processes	O
which	O
will	O
require	O
a	O
long	O
time	O
to	O
complete	O
if	O
short	O
processes	O
are	O
continually	O
added	O
.	O
</s>
<s>
Highest	B-Operating_System
response	I-Operating_System
ratio	I-Operating_System
next	I-Operating_System
is	O
similar	O
but	O
provides	O
a	O
solution	O
to	O
this	O
problem	O
using	O
a	O
technique	O
called	O
aging	B-Operating_System
.	O
</s>
<s>
Another	O
disadvantage	O
of	O
using	O
shortest	B-Operating_System
job	I-Operating_System
next	I-Operating_System
is	O
that	O
the	O
total	O
execution	O
time	O
of	O
a	O
job	O
must	O
be	O
known	O
before	O
execution	O
.	O
</s>
<s>
Multilevel	B-Operating_System
feedback	I-Operating_System
queue	I-Operating_System
can	O
also	O
be	O
used	O
to	O
approximate	O
SJN	O
without	O
the	O
need	O
for	O
the	O
total	O
execution	O
time	O
oracle	O
.	O
</s>
<s>
Shortest	B-Operating_System
job	I-Operating_System
next	I-Operating_System
can	O
be	O
effectively	O
used	O
with	O
interactive	O
processes	O
which	O
generally	O
follow	O
a	O
pattern	O
of	O
alternating	O
between	O
waiting	O
for	O
a	O
command	O
and	O
executing	O
it	O
.	O
</s>
<s>
If	O
the	O
execution	O
burst	O
of	O
a	O
process	B-Operating_System
is	O
regarded	O
as	O
a	O
separate	O
"	O
job	O
"	O
,	O
the	O
past	O
behaviour	O
can	O
indicate	O
which	O
process	B-Operating_System
to	O
run	O
next	O
,	O
based	O
on	O
an	O
estimate	O
of	O
its	O
running	O
time	O
.	O
</s>
<s>
Shortest	B-Operating_System
job	I-Operating_System
next	I-Operating_System
is	O
used	O
in	O
specialized	O
environments	O
where	O
accurate	O
estimates	O
of	O
running	O
time	O
are	O
available	O
.	O
</s>
<s>
Weighted	O
shortest	B-Operating_System
job	I-Operating_System
first	I-Operating_System
(	O
WSJF	O
)	O
is	O
a	O
modification	O
of	O
the	O
concept	O
used	O
in	O
agile	O
development	O
where	O
jobs	O
get	O
weighted	O
with	O
the	O
cost	O
of	O
delay	O
so	O
that	O
the	O
highest	O
valued	O
jobs	O
get	O
done	O
sooner	O
.	O
</s>
