<s>
A	O
distributed	B-Operating_System
database	I-Operating_System
is	O
a	O
database	O
in	O
which	O
data	O
is	O
stored	O
across	O
different	O
physical	O
locations	O
.	O
</s>
<s>
a	O
data	O
centre	O
)	O
;	O
or	O
maybe	O
dispersed	O
over	O
a	O
network	B-Architecture
of	O
interconnected	O
computers	O
.	O
</s>
<s>
Unlike	O
parallel	B-Operating_System
systems	I-Operating_System
,	O
in	O
which	O
the	O
processors	O
are	O
tightly	O
coupled	O
and	O
constitute	O
a	O
single	O
database	O
system	O
,	O
a	O
distributed	B-Operating_System
database	I-Operating_System
system	O
consists	O
of	O
loosely	O
coupled	O
sites	O
that	O
share	O
no	O
physical	O
components	O
.	O
</s>
<s>
A	O
distributed	B-Operating_System
database	I-Operating_System
can	O
reside	O
on	O
organised	O
network	B-Application
servers	I-Application
or	O
decentralised	B-Application
independent	I-Application
computers	I-Application
on	O
the	O
Internet	O
,	O
on	O
corporate	O
intranets	B-General_Concept
or	O
extranets	B-Architecture
,	O
or	O
on	O
other	O
organisation	O
networks	B-Architecture
.	O
</s>
<s>
Because	O
distributed	B-Operating_System
databases	I-Operating_System
store	O
data	O
across	O
multiple	O
computers	O
,	O
distributed	B-Operating_System
databases	I-Operating_System
may	O
improve	O
performance	O
at	O
end-user	O
worksites	O
by	O
allowing	O
transactions	O
to	O
be	O
processed	O
on	O
many	O
machines	O
,	O
instead	O
of	O
being	O
limited	O
to	O
one	O
.	O
</s>
<s>
Two	O
processes	O
ensure	O
that	O
the	O
distributed	B-Operating_System
databases	I-Operating_System
remain	O
up-to-date	O
and	O
current	O
:	O
replication	B-Architecture
and	O
duplication	O
.	O
</s>
<s>
Replication	B-Architecture
involves	O
using	O
specialized	O
software	O
that	O
looks	O
for	O
changes	O
in	O
the	O
distributive	O
database	O
.	O
</s>
<s>
Once	O
the	O
changes	O
have	O
been	O
identified	O
,	O
the	O
replication	B-Architecture
process	O
makes	O
all	O
the	O
databases	O
look	O
the	O
same	O
.	O
</s>
<s>
The	O
replication	B-Architecture
process	O
can	O
be	O
complex	O
and	O
time-consuming	O
,	O
depending	O
on	O
the	O
size	O
and	O
number	O
of	O
the	O
distributed	B-Operating_System
databases	I-Operating_System
.	O
</s>
<s>
It	O
identifies	O
one	O
database	O
as	O
a	O
master	B-Operating_System
and	O
then	O
duplicates	O
that	O
database	O
.	O
</s>
<s>
In	O
the	O
duplication	O
process	O
,	O
users	O
may	O
change	O
only	O
the	O
master	B-Operating_System
database	O
.	O
</s>
<s>
Both	O
replication	B-Architecture
and	O
duplication	O
can	O
keep	O
the	O
data	O
current	O
in	O
all	O
distributive	O
locations	O
.	O
</s>
<s>
Besides	O
distributed	B-Operating_System
database	I-Operating_System
replication	B-Architecture
and	O
fragmentation	O
,	O
there	O
are	O
many	O
other	O
distributed	B-Operating_System
database	I-Operating_System
design	O
technologies	O
.	O
</s>
<s>
For	O
example	O
,	O
local	O
autonomy	O
,	O
synchronous	O
,	O
and	O
asynchronous	O
distributed	B-Operating_System
database	I-Operating_System
technologies	O
.	O
</s>
<s>
The	O
implementation	O
of	O
these	O
technologies	O
can	O
and	O
do	O
depend	O
on	O
the	O
needs	O
of	O
the	O
business	O
and	O
the	O
sensitivity/confidentiality	O
of	O
the	O
data	O
stored	O
in	O
the	O
database	O
and	O
the	O
price	O
the	O
business	O
is	O
willing	O
to	O
spend	O
on	O
ensuring	O
data	B-General_Concept
security	I-General_Concept
,	O
consistency	B-General_Concept
and	O
integrity	O
.	O
</s>
<s>
When	O
discussing	O
access	O
to	O
distributed	B-Operating_System
databases	I-Operating_System
,	O
Microsoft	O
favors	O
the	O
term	O
distributed	O
query	O
,	O
which	O
it	O
defines	O
in	O
protocol-specific	O
manner	O
as	O
"[a]ny	O
SELECT	O
,	O
INSERT	O
,	O
UPDATE	O
,	O
or	O
DELETE	O
statement	O
that	O
references	O
tables	O
and	O
rowsets	O
from	O
one	O
or	O
more	O
external	O
OLE	O
DB	O
data	O
sources	O
"	O
.	O
</s>
<s>
Oracle	B-General_Concept
provides	O
a	O
more	O
language-centric	O
view	O
in	O
which	O
distributed	O
queries	O
and	O
distributed	B-General_Concept
transactions	I-General_Concept
form	O
part	O
of	O
distributed	O
SQL	O
.	O
</s>
