<s>
A	O
job	B-General_Concept
scheduler	I-General_Concept
is	O
a	O
computer	O
application	O
for	O
controlling	O
unattended	O
background	O
program	O
execution	O
of	O
jobs	B-General_Concept
.	O
</s>
<s>
This	O
is	O
commonly	O
called	O
batch	B-General_Concept
scheduling	I-General_Concept
,	O
as	O
execution	O
of	O
non-interactive	O
jobs	B-General_Concept
is	O
often	O
called	O
batch	B-General_Concept
processing	I-General_Concept
,	O
though	O
traditional	O
job	O
and	O
batch	O
are	O
distinguished	O
and	O
contrasted	O
;	O
see	O
that	O
page	O
for	O
details	O
.	O
</s>
<s>
Other	O
synonyms	O
include	O
batch	B-General_Concept
system	I-General_Concept
,	O
distributed	B-General_Concept
resource	I-General_Concept
management	I-General_Concept
system	I-General_Concept
(	O
DRMS	O
)	O
,	O
distributed	B-General_Concept
resource	I-General_Concept
manager	I-General_Concept
(	O
DRM	O
)	O
,	O
and	O
,	O
commonly	O
today	O
,	O
workload	B-General_Concept
automation	I-General_Concept
(	O
WLA	O
)	O
.	O
</s>
<s>
The	O
data	O
structure	O
of	O
jobs	B-General_Concept
to	O
run	O
is	O
known	O
as	O
the	O
job	B-General_Concept
queue	I-General_Concept
.	O
</s>
<s>
Modern	O
job	B-General_Concept
schedulers	I-General_Concept
typically	O
provide	O
a	O
graphical	O
user	O
interface	O
and	O
a	O
single	O
point	O
of	O
control	O
for	O
definition	O
and	O
monitoring	O
of	O
background	O
executions	O
in	O
a	O
distributed	O
network	O
of	O
computers	O
.	O
</s>
<s>
Increasingly	O
,	O
job	B-General_Concept
schedulers	I-General_Concept
are	O
required	O
to	O
orchestrate	O
the	O
integration	O
of	O
real-time	O
business	O
activities	O
with	O
traditional	O
background	O
IT	O
processing	O
across	O
different	O
operating	B-General_Concept
system	I-General_Concept
platforms	O
and	O
business	O
application	O
environments	O
.	O
</s>
<s>
Job	B-General_Concept
scheduling	I-General_Concept
should	O
not	O
be	O
confused	O
with	O
process	O
scheduling	O
,	O
which	O
is	O
the	O
assignment	O
of	O
currently	O
running	O
processes	O
to	O
CPUs	B-Device
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Basic	O
features	O
expected	O
of	O
job	B-General_Concept
scheduler	I-General_Concept
software	O
include	O
:	O
</s>
<s>
If	O
software	O
from	O
a	O
completely	O
different	O
area	O
includes	O
all	O
or	O
some	O
of	O
those	O
features	O
,	O
this	O
software	O
can	O
be	O
considered	O
to	O
have	O
job	B-General_Concept
scheduling	I-General_Concept
capabilities	O
.	O
</s>
<s>
Most	O
operating	B-General_Concept
systems	I-General_Concept
,	O
such	O
as	O
Unix	B-Application
and	O
Windows	B-Application
,	O
provide	O
basic	O
job	B-General_Concept
scheduling	I-General_Concept
capabilities	O
,	O
notably	O
by	O
at	B-Device
and	I-Device
batch	I-Device
,	O
cron	B-General_Concept
,	O
and	O
the	O
Windows	B-Application
Task	O
Scheduler	O
.	O
</s>
<s>
Web	O
hosting	O
services	O
provide	O
job	B-General_Concept
scheduling	I-General_Concept
capabilities	O
through	O
a	O
control	B-Application
panel	I-Application
or	O
a	O
webcron	B-Application
solution	I-Application
.	O
</s>
<s>
Many	O
programs	O
such	O
as	O
DBMS	B-Application
,	O
backup	B-Protocol
,	O
ERPs	O
,	O
and	O
BPM	O
also	O
include	O
relevant	O
job-scheduling	O
capabilities	O
.	O
</s>
<s>
Operating	B-General_Concept
system	I-General_Concept
(	O
"	O
OS	O
"	O
)	O
or	O
point	O
program	O
supplied	O
job-scheduling	O
will	O
not	O
usually	O
provide	O
the	O
ability	O
to	O
schedule	O
beyond	O
a	O
single	O
OS	O
instance	O
or	O
outside	O
the	O
remit	O
of	O
the	O
specific	O
program	O
.	O
</s>
<s>
Organizations	O
needing	O
to	O
automate	O
unrelated	O
IT	O
workload	O
may	O
also	O
leverage	O
further	O
advanced	O
features	O
from	O
a	O
job	B-General_Concept
scheduler	I-General_Concept
,	O
such	O
as	O
:	O
</s>
<s>
These	O
advanced	O
capabilities	O
can	O
be	O
written	O
by	O
in-house	O
developers	O
but	O
are	O
more	O
often	O
provided	O
by	O
suppliers	O
who	O
specialize	O
in	O
systems-management	B-Application
software	O
.	O
</s>
<s>
There	O
are	O
many	O
concepts	O
that	O
are	O
central	O
to	O
almost	O
every	O
job	B-General_Concept
scheduler	I-General_Concept
implementation	O
and	O
that	O
are	O
widely	O
recognized	O
with	O
minimal	O
variations	O
:	O
Jobs	B-General_Concept
,	O
Dependencies	O
,	O
Job	O
Streams	O
,	O
and	O
Users	O
.	O
</s>
<s>
Beyond	O
the	O
basic	O
,	O
single	O
OS	O
instance	O
scheduling	O
tools	O
there	O
are	O
two	O
major	O
architectures	O
that	O
exist	O
for	O
Job	B-General_Concept
Scheduling	I-General_Concept
software	O
.	O
</s>
<s>
Master/Agent	O
architecture	O
—	O
the	O
historic	O
architecture	O
for	O
Job	B-General_Concept
Scheduling	I-General_Concept
software	O
.	O
</s>
<s>
The	O
Job	B-General_Concept
Scheduling	I-General_Concept
software	O
is	O
installed	O
on	O
a	O
single	O
machine	O
(	O
Master	O
)	O
,	O
while	O
on	O
production	O
machines	O
only	O
a	O
very	O
small	O
component	O
(	O
Agent	O
)	O
is	O
installed	O
that	O
awaits	O
commands	O
from	O
the	O
Master	O
,	O
executes	O
them	O
,	O
then	O
returns	O
the	O
exit	O
code	O
back	O
to	O
the	O
Master	O
.	O
</s>
<s>
Cooperative	O
architecture	O
—	O
a	O
decentralized	O
model	O
where	O
each	O
machine	O
is	O
capable	O
of	O
helping	O
with	O
scheduling	O
and	O
can	O
offload	O
locally	O
scheduled	O
jobs	B-General_Concept
to	O
other	O
cooperating	O
machines	O
.	O
</s>
<s>
Job	B-General_Concept
Scheduling	I-General_Concept
has	O
a	O
long	O
history	O
.	O
</s>
<s>
Job	B-General_Concept
Schedulers	I-General_Concept
have	O
been	O
one	O
of	O
the	O
major	O
components	O
of	O
IT	B-Application
infrastructure	I-Application
since	O
the	O
early	O
mainframe	O
systems	O
.	O
</s>
<s>
At	O
first	O
,	O
stacks	O
of	O
punched	B-Architecture
cards	I-Architecture
were	O
processed	O
one	O
after	O
the	O
other	O
,	O
hence	O
the	O
term	O
"	O
batch	B-General_Concept
processing	I-General_Concept
"	O
.	O
</s>
<s>
From	O
a	O
historical	O
point	O
of	O
view	O
,	O
we	O
can	O
distinguish	O
two	O
main	O
eras	O
about	O
Job	B-General_Concept
Schedulers	I-General_Concept
:	O
</s>
<s>
Job	B-Application
Control	I-Application
Language	I-Application
(	O
JCL	O
)	O
on	O
IBM	B-Device
mainframes	I-Device
.	O
</s>
<s>
Initially	O
based	O
on	O
JCL	O
functionality	O
to	O
handle	O
dependencies	O
,	O
this	O
era	O
is	O
typified	O
by	O
the	O
development	O
of	O
sophisticated	O
scheduling	O
solutions	O
(	O
such	O
as	O
Job	B-Application
Entry	I-Application
Subsystem	I-Application
2/3	I-Application
)	O
forming	O
part	O
of	O
the	O
systems	B-Application
management	I-Application
and	O
automation	O
toolset	O
on	O
the	O
mainframe	O
.	O
</s>
<s>
Modern	O
schedulers	O
on	O
a	O
variety	O
of	O
architectures	O
and	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
With	O
standard	O
scheduling	O
tools	O
limited	O
to	O
commands	O
such	O
as	O
at	B-Device
and	I-Device
batch	I-Device
,	O
the	O
need	O
for	O
mainframe	O
standard	O
job	B-General_Concept
schedulers	I-General_Concept
has	O
grown	O
with	O
the	O
increased	O
adoption	O
of	O
distributed	B-Architecture
computing	I-Architecture
environments	O
.	O
</s>
<s>
Batch	B-General_Concept
processing	I-General_Concept
-	O
the	O
traditional	O
date	O
and	O
time	O
based	O
execution	O
of	O
background	O
tasks	O
based	O
on	O
a	O
defined	O
period	O
during	O
which	O
resources	O
were	O
available	O
for	O
batch	B-General_Concept
processing	I-General_Concept
(	O
the	O
batch	O
window	O
)	O
.	O
</s>
<s>
In	O
effect	O
the	O
original	O
mainframe	O
approach	O
transposed	O
onto	O
the	O
open	B-Operating_System
systems	I-Operating_System
environment	O
.	O
</s>
<s>
Service	O
Oriented	O
job	B-General_Concept
scheduling	I-General_Concept
-	O
recent	O
developments	O
in	O
Service	O
Oriented	O
Architecture	O
(	O
SOA	O
)	O
have	O
seen	O
a	O
move	O
towards	O
deploying	O
job	B-General_Concept
scheduling	I-General_Concept
as	O
a	O
reusable	O
IT	B-Application
infrastructure	I-Application
service	O
that	O
can	O
play	O
a	O
role	O
in	O
the	O
integration	O
of	O
existing	O
business	O
application	O
workload	O
with	O
new	O
Web	O
Services	O
based	O
real-time	O
applications	O
.	O
</s>
