<s>
Database	B-Application
tables	I-Application
and	O
indexes	B-Data_Structure
may	O
be	O
stored	O
on	O
disk	O
in	O
one	O
of	O
a	O
number	O
of	O
forms	O
,	O
including	O
ordered/unordered	O
flat	B-Application
files	I-Application
,	O
ISAM	B-Application
,	O
heap	B-Application
files	O
,	O
hash	B-Algorithm
buckets	I-Algorithm
,	O
or	O
B+	O
trees	O
.	O
</s>
<s>
The	O
most	O
commonly	O
used	O
forms	O
are	O
B-trees	B-Architecture
and	O
ISAM	B-Application
.	O
</s>
<s>
Such	O
forms	O
or	O
structures	O
are	O
one	O
aspect	O
of	O
the	O
overall	O
schema	O
used	O
by	O
a	O
database	B-General_Concept
engine	I-General_Concept
to	O
store	O
information	O
.	O
</s>
<s>
Such	O
storage	O
offers	O
good	O
insertion	O
efficiency	B-General_Concept
(	O
)	O
,	O
but	O
inefficient	O
retrieval	O
times	O
(	O
)	O
.	O
</s>
<s>
Typically	O
these	O
retrieval	O
times	O
are	O
better	O
,	O
however	O
,	O
as	O
most	O
databases	O
use	O
indexes	B-Data_Structure
on	O
the	O
primary	B-Application
keys	I-Application
,	O
resulting	O
in	O
retrieval	O
times	O
of	O
or	O
for	O
keys	O
that	O
are	O
the	O
same	O
as	O
the	O
database	O
row	O
offsets	O
within	O
the	O
storage	O
system	O
.	O
</s>
<s>
Ordered	O
storage	O
typically	O
stores	O
the	O
records	O
in	O
order	O
and	O
may	O
have	O
to	O
rearrange	O
or	O
increase	O
the	O
file	O
size	O
when	O
a	O
new	O
record	O
is	O
inserted	O
,	O
resulting	O
in	O
lower	O
insertion	O
efficiency	B-General_Concept
.	O
</s>
<s>
Heap	B-Application
files	O
are	O
lists	O
of	O
unordered	O
records	O
of	O
variable	O
size	O
.	O
</s>
<s>
Although	O
sharing	O
a	O
similar	O
name	O
,	O
heap	B-Application
files	O
are	O
widely	O
different	O
from	O
in-memory	O
heaps	B-Application
.	O
</s>
<s>
In-memory	O
heaps	B-Application
are	O
ordered	O
,	O
as	O
opposed	O
to	O
heap	B-Application
files	O
.	O
</s>
<s>
Most	O
conventional	O
relational	B-Application
databases	I-Application
use	O
"	O
row-oriented	O
"	O
storage	O
,	O
meaning	O
that	O
all	O
data	O
associated	O
with	O
a	O
given	O
row	O
is	O
stored	O
together	O
.	O
</s>
<s>
By	O
contrast	O
,	O
column-oriented	B-General_Concept
DBMS	I-General_Concept
store	O
all	O
data	O
from	O
a	O
given	O
column	O
together	O
in	O
order	O
to	O
more	O
quickly	O
serve	O
data	O
warehouse-style	O
queries	O
.	O
</s>
