<s>
Archive	O
is	O
a	O
storage	B-General_Concept
engine	I-General_Concept
for	O
the	O
MySQL	B-Application
relational	B-Application
database	I-Application
management	I-Application
system	I-Application
.	O
</s>
<s>
Users	O
can	O
use	O
this	O
analytic	O
storage	B-General_Concept
engine	I-General_Concept
to	O
create	O
a	O
table	O
that	O
is	O
“	O
archive	O
”	O
only	O
.	O
</s>
<s>
The	O
Archive	O
engine	O
uses	O
a	O
compression	O
strategy	O
based	O
on	O
the	O
zlib	B-Language
library	O
and	O
it	O
packs	O
the	O
rows	O
using	O
a	O
bit	O
header	O
to	O
represent	O
nulls	O
and	O
removes	O
all	O
whitespace	O
for	O
character	O
type	O
fields	O
.	O
</s>
<s>
Archive	O
tables	O
,	O
however	O
,	O
are	O
supported	O
by	O
the	O
MySQL	B-Application
Query	O
Cache	O
,	O
which	O
can	O
dramatically	O
reduce	O
response	O
times	O
for	O
Archive	O
table	O
queries	O
that	O
are	O
repetitively	O
issued	O
.	O
</s>
<s>
MySQL	B-Application
is	O
examining	O
index	O
support	O
for	O
Archive	O
tables	O
in	O
upcoming	O
releases	O
.	O
</s>
<s>
Unlike	O
OLTP	B-General_Concept
engines	O
,	O
it	O
uses	O
a	O
"	O
stream	O
"	O
format	O
to	O
disk	O
with	O
no	O
block	O
boundaries	O
.	O
</s>
<s>
In	O
MySQL	B-Application
5.1	I-Application
,	O
a	O
copy	O
of	O
the	O
MySQL	B-Application
FRM	O
file	O
is	O
stored	O
in	O
the	O
header	O
of	O
each	O
Archive	O
file	O
.	O
</s>
<s>
The	O
FRM	O
file	O
,	O
which	O
represents	O
the	O
definition	O
of	O
a	O
table	O
,	O
allows	O
an	O
Archive	O
file	O
to	O
be	O
restored	O
to	O
a	O
MySQL	B-Application
server	I-Application
if	O
the	O
Archive	O
file	O
is	O
copied	O
to	O
the	O
server	O
.	O
</s>
<s>
Despite	O
the	O
use	O
of	O
zlib	B-Language
,	O
archive	O
files	O
are	O
not	O
compatible	O
with	O
gzio	O
,	O
the	O
basis	O
of	O
the	O
gzip	B-Application
tools	O
.	O
</s>
<s>
Archive	O
differs	O
from	O
the	O
other	O
MySQL	B-Application
analytical	O
engine	O
,	O
MyISAM	B-Language
,	O
by	O
being	O
a	O
row-level	O
locking	O
engine	O
and	O
by	O
keeping	O
a	O
constant	O
version	O
snapshot	O
throughout	O
a	O
single	O
query	O
(	O
making	O
it	O
MVCC	B-Operating_System
)	O
.	O
</s>
<s>
For	O
bulk	O
inserts	O
it	O
performs	O
an	O
interlaced	O
INSERT	O
,	O
so	O
unlike	O
MyISAM	B-Language
,	O
order	O
is	O
not	O
guaranteed	O
.	O
</s>
<s>
The	O
MySQL	B-Language
Archive	I-Language
Storage	B-General_Concept
Engine	I-General_Concept
was	O
authored	O
and	O
is	O
maintained	O
by	O
Brian	O
Aker	O
.	O
</s>
<s>
It	O
was	O
introduced	O
in	O
2004	O
with	O
MySQL	B-Application
4.1	O
.	O
</s>
