<s>
A	O
track	O
,	O
session	O
or	O
title	O
on	O
an	O
audiovideo	O
optical	B-Device
disk	I-Device
is	O
a	O
segment	O
recording	O
a	O
single	O
movement	O
,	O
song	O
or	O
other	O
work	O
.	O
</s>
<s>
Five	O
level	O
tape	O
is	O
used	O
for	O
Baudot	O
,	O
eight-level	O
for	O
ASCII	B-Protocol
and	O
twelve	O
level	O
for	O
carriage	B-Device
control	I-Device
tapes	I-Device
.	O
</s>
<s>
The	O
NCR	B-Device
CRAM	I-Device
,	O
RCA	O
Model	O
3488	O
Random	O
Access	O
Computer	O
Equipment	O
and	O
RCA	O
70/568	O
-11	O
Mass	B-Device
Storage	I-Device
Unitused	O
magnetic	O
cards	O
in	O
a	O
magazine	O
(	O
deck	O
for	O
CRAM	O
)	O
.inch	O
)	O
.	O
</s>
<s>
The	O
IBM	B-Device
2321	I-Device
Data	I-Device
Cell	I-Device
used	O
magnetic	O
strips	O
in	O
a	O
cell	O
and	O
subcell	O
.	O
</s>
<s>
The	O
tracks	O
had	O
variable	O
length	O
count	B-Application
key	I-Application
data	I-Application
(	O
CKD	O
)	O
records	O
.	O
</s>
<s>
An	O
example	O
is	O
the	O
IBM	B-Device
3850	I-Device
Mass	I-Device
Storage	I-Device
System	I-Device
(	O
MSS	O
)	O
.	O
</s>
<s>
However	O
,	O
some	O
older	O
disks	O
and	O
drums	O
recorded	O
variable	O
length	O
records	O
,	O
and	O
the	O
DASD	B-Application
subsystems	O
supported	O
for	O
general	O
use	O
by	O
IBM	O
's	O
flagship	O
operating	O
systems	O
simulate	O
the	O
Count	B-Application
Key	I-Application
Data	I-Application
(	O
CKD	O
)	O
organization	O
.	O
</s>
<s>
Drums	O
used	O
for	O
auxiliary	O
storage	O
typically	O
had	O
fixed	O
length	O
sectors	O
,	O
but	O
the	O
IBM	O
7320	O
on	O
the	O
IBM	B-Device
7090	I-Device
and	O
7094	O
had	O
variable	O
length	O
records	O
controlled	O
by	O
a	O
format	O
track	O
and	O
the	O
IBM	O
2301	O
,	O
2303	O
and	O
7320	O
on	O
the	O
S/360	B-Application
had	O
variable	O
length	O
CKD	O
records	O
.	O
</s>
<s>
Most	O
of	O
the	O
industry	O
designed	O
disk	O
drives	O
with	O
fixed	O
length	O
sectors	O
,	O
however	O
the	O
IBM	B-Device
1301	I-Device
and	O
IBM	B-Device
1302	I-Device
on	O
the	O
7000	B-Device
series	I-Device
had	O
variable	O
length	O
records	O
controlled	O
by	O
format	O
tracks	O
and	O
all	O
DASD	B-Application
on	O
S/360	B-Application
had	O
variable	O
length	O
CKD	O
records	O
.	O
</s>
<s>
Although	O
IBM	O
supports	O
FBA	B-Device
and	O
SCSI	B-Architecture
disk	O
drives	O
on	O
IBM	B-Device
Z	I-Device
,	O
its	O
flagship	O
z/OS	B-Application
operating	O
system	O
only	O
has	O
limited	O
support	O
for	O
SCSI	B-Architecture
drives	O
and	O
requires	O
CKD	O
drives	O
for	O
most	O
functions	O
.	O
</s>
<s>
Starting	O
with	O
the	O
3350	B-Device
,	O
IBM	O
offered	O
disc	O
drives	O
with	O
new	O
geometries	O
that	O
could	O
present	O
the	O
appearance	O
of	O
older	O
disk	O
drives	O
.	O
</s>
<s>
At	O
the	O
present	O
time	O
almost	O
all	O
IBM	O
mainframes	O
use	O
DASD	B-Application
subsystems	O
that	O
look	O
like	O
3390	B-Device
drives	O
but	O
use	O
SCSI	B-Architecture
disks	O
and	O
SSDs	B-Device
to	O
actually	O
store	O
the	O
data	O
.	O
</s>
