<s>
A	O
definitive	O
media	O
library	O
is	O
a	O
secure	O
information	B-General_Concept
technology	I-General_Concept
repository	O
in	O
which	O
an	O
organisation	O
's	O
definitive	O
,	O
authorised	O
versions	O
of	O
software	O
media	O
are	O
stored	O
and	O
protected	O
.	O
</s>
<s>
The	O
Definitive	O
Media	O
Library	O
provides	O
the	O
storage	O
area	O
for	O
software	O
objects	O
ready	O
for	O
deployment	O
and	O
should	O
only	O
contain	O
master	O
copies	O
of	O
controlled	O
software	O
media	O
configuration	O
items	O
(	O
CIs	O
)	O
that	O
have	O
passed	O
appropriate	O
quality	O
assurance	O
checks	O
,	O
typically	O
including	O
both	O
procured	O
and	O
bespoke	O
application	O
and	O
gold	O
build	O
source	O
code	O
and	O
executables	B-Application
.	O
</s>
<s>
In	O
the	O
context	O
of	O
the	O
ITIL	O
best	O
practice	O
framework	O
,	O
the	O
term	O
definitive	O
media	O
library	O
supersedes	O
the	O
term	O
definitive	B-Device
software	I-Device
library	I-Device
referred	O
to	O
prior	O
to	O
version	O
ITIL	O
v3	O
.	O
</s>
<s>
In	O
conjunction	O
with	O
the	O
configuration	B-Application
management	I-Application
database	I-Application
(	O
CMDB	B-Application
)	O
,	O
it	B-General_Concept
effectively	O
provides	O
the	O
DNA	O
of	O
the	O
data	B-Operating_System
center	I-Operating_System
i.e.	O
</s>
<s>
all	O
application	O
and	O
build	O
software	O
media	O
connected	O
to	O
the	O
CMDB	B-Application
record	O
of	O
installation	O
and	O
configuration	O
.	O
</s>
<s>
In	O
a	O
controlled	O
IT	B-General_Concept
environment	O
it	B-General_Concept
is	O
crucial	O
that	O
only	O
authorised	O
versions	O
of	O
software	O
are	O
allowed	O
into	O
production	O
.	O
</s>
<s>
The	O
solution	O
put	O
forward	O
by	O
ITIL	O
in	O
its	O
third	O
version	O
is	O
called	O
the	O
definitive	O
media	O
library	O
or	O
DML	O
(	O
replacing	O
the	O
previously	O
named	O
Definitive	B-Device
Software	I-Device
Library	I-Device
or	O
DSL	O
in	O
version	O
two	O
)	O
.	O
</s>
<s>
software	O
required	O
to	O
be	O
deployed	O
into	O
production	O
should	O
be	O
rigorously	O
tested	O
,	O
assured	O
and	O
licensed	O
to	O
perform	O
and	O
also	O
packaged	O
in	O
such	O
a	O
way	O
that	O
it	B-General_Concept
will	O
safely	O
and	O
consistently	O
deploy	O
.	O
</s>
<s>
records	O
(	O
metadata	O
)	O
are	O
kept	O
in	O
a	O
configuration	B-Application
management	I-Application
database	I-Application
about	O
where	O
the	O
software	O
is	O
installed	O
and	O
deployed	O
from	O
the	O
DML	O
and	O
into	O
the	O
production	O
environment	O
.	O
</s>
<s>
Each	O
installation	O
or	O
deployment	O
should	O
be	O
authorised	O
by	O
a	O
corresponding	O
production	O
change	O
request	O
and	O
the	O
resulting	O
change	O
recorded	O
in	O
the	O
configuration	B-Application
management	I-Application
database	I-Application
as	O
a	O
relationship	O
between	O
the	O
DML	O
artefact	O
and	O
the	O
platform	O
where	O
it	B-General_Concept
has	O
been	O
deployed	O
.	O
</s>
<s>
Following	O
Change	O
Management	O
approval	O
,	O
product	O
is	O
released	O
to	O
the	O
estate	O
via	O
the	O
appropriate	O
distribution	O
system	O
with	O
logical	O
installations	O
being	O
recorded	O
via	O
due	O
process	O
in	O
the	O
CMS	O
(	O
CMDB	B-Application
)	O
.	O
</s>
