<s>
9-track	B-Device
tape	I-Device
is	O
a	O
format	O
for	O
magnetic-tape	B-Architecture
data	I-Architecture
storage	I-Architecture
,	O
introduced	O
with	O
the	O
IBM	B-Application
System/360	I-Application
in	O
1964	O
.	O
</s>
<s>
The	O
wide	O
magnetic	O
tape	O
media	O
and	O
reels	O
have	O
the	O
same	O
size	O
as	O
the	O
earlier	O
IBM	B-Device
7-track	I-Device
format	O
it	O
replaced	O
,	O
but	O
the	O
new	O
format	O
has	O
eight	O
data	O
tracks	O
and	O
one	O
parity	B-Error_Name
track	O
for	O
a	O
total	O
of	O
nine	O
parallel	O
tracks	O
.	O
</s>
<s>
Data	O
is	O
stored	O
as	O
8-bit	O
characters	O
,	O
spanning	O
the	O
full	O
width	O
of	O
the	O
tape	O
(	O
including	O
the	O
parity	B-Error_Name
bit	I-Error_Name
)	O
.	O
</s>
<s>
Various	O
recording	O
methods	O
have	O
been	O
employed	O
during	O
its	O
lifetime	O
as	O
tape	O
speed	O
and	O
data	O
density	O
increased	O
,	O
including	O
PE	B-Protocol
(	O
phase	B-Protocol
encoding	I-Protocol
)	O
,	O
GCR	B-Device
(	O
group-coded	B-Device
recording	I-Device
)	O
and	O
NRZI	O
(	O
non-return-to-zero	O
,	O
inverted	O
,	O
sometimes	O
pronounced	O
"	O
nur-zee	O
"	O
)	O
.	O
</s>
<s>
The	O
standard	O
size	O
of	O
a	O
byte	B-Application
was	O
effectively	O
set	O
at	O
eight	O
bits	O
with	O
the	O
S/360	B-Application
and	O
nine-track	B-Device
tape	I-Device
.	O
</s>
<s>
A	O
typical	O
9-track	B-Device
unit	O
consists	O
of	O
a	O
tape	O
transport	O
—	O
essentially	O
all	O
the	O
mechanics	O
that	O
moves	O
tape	O
from	O
reel	O
to	O
reel	O
past	O
the	O
read/write	O
and	O
erase	O
heads	O
—	O
and	O
supporting	O
control	O
and	O
data	O
read/write	O
electronics	O
.	O
</s>
<s>
The	O
transport	O
typically	O
consists	O
of	O
supply	O
motor	O
,	O
take-up	O
motor	O
,	O
hubs	O
for	O
locking	O
the	O
tape	O
reels	O
in	O
place	O
,	O
a	O
capstan	O
motor	O
(	O
though	O
not	O
necessarily	O
a	O
pinch	O
roller	O
,	O
see	O
below	O
)	O
,	O
tape	O
head	O
assembly	O
,	O
miscellaneous	O
rollers	O
which	O
keep	O
the	O
tape	O
in	O
a	O
precise	O
path	O
during	O
operation	O
,	O
and	O
vacuum	B-Device
columns	I-Device
which	O
prevent	O
tape	O
'	O
snatch	O
 '	O
.	O
</s>
<s>
Feedback	O
to	O
the	O
control	O
electronics	O
is	O
accomplished	O
by	O
a	O
tachometer	B-Device
,	O
usually	O
an	O
optical	O
"	O
tone	O
wheel	O
"	O
,	O
to	O
control	O
tape	O
velocity	O
.	O
</s>
<s>
The	O
vacuum	O
system	O
provides	O
a	O
physical	O
buffer	O
between	O
the	O
precision	O
movements	O
of	O
the	O
capstan	O
and	O
the	O
large	O
movements	O
of	O
the	O
reels	O
by	O
storing	O
a	O
short	O
length	O
of	O
tape	O
in	O
the	O
vacuum	B-Device
column	I-Device
under	O
relatively	O
low	O
tension	O
.	O
</s>
<s>
The	O
vacuum	B-Device
columns	I-Device
are	O
chambers	O
open	O
at	O
one	O
end	O
,	O
the	O
openings	O
being	O
in	O
line	O
with	O
the	O
tape	O
path	O
before	O
and	O
after	O
the	O
capstan	O
and	O
roller	O
assemblies	O
.	O
</s>
<s>
Because	O
of	O
the	O
tension	O
provided	O
by	O
the	O
vacuum	B-Device
columns	I-Device
and	O
the	O
design	O
of	O
the	O
tape	O
path	O
,	O
tape	O
is	O
usually	O
kept	O
in	O
sufficient	O
contact	O
with	O
the	O
relatively	O
high-friction	O
coating	O
on	O
the	O
capstan	O
that	O
a	O
pinch	O
roller	O
is	O
not	O
used	O
.	O
</s>
<s>
Because	O
the	O
supply	O
vacuum	B-Device
column	I-Device
keeps	O
a	O
small	O
,	O
constant	O
tension	O
in	O
the	O
reverse	O
direction	O
,	O
the	O
capstan	O
can	O
feed	O
backwards	O
without	O
the	O
tape	O
bunching	O
up	O
or	O
jumping	O
out	O
of	O
its	O
path	O
.	O
</s>
<s>
This	O
is	O
the	O
main	O
reason	O
that	O
photographic	O
flash	O
cameras	O
are	O
not	O
allowed	O
in	O
data	O
centers	O
with	O
9-track	B-Device
tape	I-Device
drives	O
since	O
they	O
can	O
trick	O
the	O
tape	O
drives	O
into	O
falsely	O
sensing	O
BOT	O
and	O
EOT	O
.	O
</s>
<s>
Some	O
designs	O
eliminate	O
the	O
vacuum	B-Device
columns	I-Device
in	O
favor	O
of	O
a	O
microprocessor-controlled	O
direct	O
drive	O
design	O
.	O
</s>
<s>
9-track	B-Device
800	O
NRZI	O
and	O
1600	O
PE	B-Protocol
(	O
phase	B-Protocol
encoding	I-Protocol
)	O
tapes	O
use	O
a	O
inter-record	O
gap	O
(	O
IRG	O
)	O
between	O
data	O
records	O
to	O
allow	O
the	O
tape	O
to	O
stop	O
and	O
start	O
between	O
records	O
.	O
</s>
<s>
6250	O
GCR	B-Device
tapes	O
use	O
a	O
tighter	O
IRG	O
.	O
</s>
<s>
9-track	B-Device
tapes	I-Device
have	O
reflective	O
stickers	O
placed	O
on	O
the	O
non-data	O
side	O
from	O
the	O
beginning	O
of	O
the	O
tape	O
and	O
from	O
the	O
end	O
of	O
the	O
tape	O
to	O
facilitate	O
signaling	O
the	O
hardware	O
to	O
prevent	O
the	O
tape	O
from	O
unwinding	O
from	O
the	O
hubs	O
.	O
</s>
<s>
Nine-track	B-Device
tapes	I-Device
have	O
densities	O
of	O
800	O
,	O
1600	O
,	O
and	O
6250	O
8-bit	O
bytes	B-Application
per	O
inch	O
,	O
giving	O
approximately	O
22.5MB	O
,	O
45MB	O
and	O
175MB	O
respectively	O
on	O
a	O
tape	O
with	O
the	O
usual	O
length	O
of	O
.	O
</s>
<s>
The	O
2400	O
Series	O
Magnetic	O
Tape	O
Units	O
were	O
introduced	O
with	O
the	O
System/360	B-Application
and	O
were	O
the	O
first	O
to	O
use	O
9	B-Device
track	I-Device
tape	I-Device
.	O
</s>
<s>
The	O
dimensions	O
of	O
the	O
tape	O
and	O
reels	O
are	O
identical	O
to	O
those	O
used	O
with	O
7	B-Device
track	I-Device
units	O
,	O
such	O
as	O
the	O
IBM	B-Device
729	I-Device
.	O
</s>
<s>
But	O
older	O
7	B-Device
track	I-Device
tapes	I-Device
can	O
be	O
read	O
and	O
written	O
only	O
on	O
special	O
2400	O
drives	O
equipped	O
with	O
7	B-Device
track	I-Device
read	O
and	O
write	O
heads	O
and	O
the	O
7	B-Device
track	I-Device
compatibility	O
option	O
.	O
</s>
<s>
The	O
3400	O
Series	O
Magnetic	O
Tape	O
Units	O
were	O
introduced	O
with	O
the	O
IBM	B-Device
System/370	I-Device
.	O
</s>
<s>
While	O
the	O
earlier	O
tape	O
drives	O
have	O
vacuum	B-Device
columns	I-Device
,	O
some	O
IBM	O
tape	O
drives	O
such	O
as	O
the	O
8809	O
drive	O
(	O
1980	O
's	O
)	O
have	O
a	O
flat	O
mount	O
situation	O
and	O
no	O
vacuum	B-Device
columns	I-Device
exist	O
.	O
</s>
<s>
The	O
maximum	O
data	O
capacity	O
of	O
a	O
2400ft	O
reel	O
,	O
with	O
32,767	O
byte	B-Application
blocks	O
and	O
recorded	O
at	O
6250	O
BPI	O
is	O
170megabytes	O
.	O
</s>
<s>
Typically	O
,	O
much	O
smaller	O
block	O
sizes	O
,	O
such	O
as	O
4K	O
(	O
4,096	O
bytes	B-Application
)	O
are	O
used	O
,	O
in	O
which	O
case	O
the	O
storage	O
capacity	O
of	O
the	O
tape	O
is	O
reduced	O
to	O
113megabytes	O
.	O
</s>
<s>
Depending	O
on	O
the	O
operating	O
system	O
,	O
tapes	O
are	O
formatted	O
as	O
either	O
EBCDIC	B-Language
(	O
if	O
IBM	O
equipment	O
is	O
used	O
)	O
or	O
ASCII	O
,	O
and	O
are	O
either	O
"	O
labeled	O
"	O
(	O
if	O
the	O
data	O
is	O
preceded	O
by	O
a	O
tape	O
header	O
,	O
typically	O
containing	O
a	O
tape	O
name	O
and	O
date	O
)	O
,	O
"	O
unlabeled	O
"	O
(	O
if	O
the	O
tape	O
contains	O
no	O
header	O
)	O
or	O
have	O
a	O
"	O
non-standard	O
label	O
"	O
(	O
the	O
tape	O
has	O
a	O
header	O
,	O
but	O
it	O
does	O
not	O
conform	O
to	O
the	O
format	O
expected	O
by	O
the	O
equipment	O
used	O
to	O
read	O
the	O
tape	O
)	O
.	O
</s>
<s>
STC	O
/	O
Storage	B-Application
Technology	I-Application
Corp	O
,	O
(	O
then	O
:	O
StorageTek	B-Application
(	O
STK	O
)	O
after	O
name	O
change	O
)	O
,	O
(	O
acquired	O
by	O
SUN	O
,	O
now	O
a	O
division	O
of	O
Oracle	O
Corp	O
)	O
.	O
</s>
<s>
3M	O
now	O
Imation	O
—	O
The	O
first	O
manufacturer	O
of	O
9	B-Device
track	I-Device
tape	I-Device
.	O
</s>
<s>
Graham	O
Magnetics	O
—	O
The	O
last	O
manufacturer	O
to	O
produce	O
new	O
9-track	B-Device
tape	I-Device
(	O
2001	O
)	O
.	O
</s>
