Volume Label Format - IBM 5280 Maintenance Information Manual

Volume Label Format
The volume label is located at track 00, head 0, record 7
on all diskettes. This label identifies the diskette and
indicates to the diskette control circuitry how the informa-
tion on the diskette is arranged. The volume label is
encoded on the diskette every time the diskette initialization
utility program is used to initialize the diskette. The
volume label is always encoded in FM format. This label
is read and verified each time a Sense command is issued
to the diskette drive.
Volume Label Fields
Volume Label Identifier and Number (bytes 0 through 3):
Identifies this portion of the diskette as a volume label,
for example, VOL 1.
Volume Identifier as Specified By the User (bytes 4
through 9):
Identifies the diskette. This field contains up
to six alphameric characters, and is specified during
diskette initialization.
Accessibility (byte 10): Indicates if the diskette can be
read from or written to. A blank in this field permits
access to the information on the diskette. Any other
character in this field prohibits access.
Not Used (bytes
11
through 36):
Owner Identification (bytes 37 through 50): Identifies
the owner of the diskette or the owner of the information
on the diskette. This field contains 14 alphameric
characters.
Not Used (bytes 51 through 63):
Extended Label Area (byte 64):
Indicates how many, if
any, additional tracks have been allocated as header label
tracks. Up to nine (9) additional tracks on each side of a
diskette 20 can be set aside for additional header labels.
For example: 0
=
no additional tracks, 1
=
one additional
track, and so on.
Not Used (bytes 65 through 70):
Volume Surface Indicator (byte 71):
Identifies the
diskette as a diskette 1, diskette 2, or diskette 20.
space
2
M
diskette 1
diskette 2
diskette 20
Extent Arrangement Indicator (byte 72): Indicates if there
are any constrai nts on the arrangement of extents, data
set labels, or unallocated space on this diskette as follows:
p
= •
Extents must be adjacent
• Extents must start at cylinder 1, head 0,
sector 1
• Data set labels must start at cylinder 1, head 0,
sector 1
• Data set labels must be in the same sequence as
the extents they describe
• All unallocated space must follow the last data
set extent
Blank
=
No constraints
Special Requirements Indicator (byte 73):
Indicates if
there are any special requirements for accessing data on
this volume. A blank indicates that there are no special
requirements. An R indicates that some of the data sets
were recorded in a logically nonsequential manner.
Not Used (byte 74):
Physical Sector Length (byte 75):
Identifies the length of
the physical record (sector) on cylinder 1 through 76.
blank
1
2
3
=
128 bytes
=256 bytes
=
512 bytes
=
1024 bytes
Theory 67