Chapter 8. Disk Initialization - IBM 3741 Data Station Reference Manual

All disks are initialized before they are shipped to a
customer. Reinitializing should be avoided unless neces-
sary; it is requi'red only if:
1.
2.
3.
The disk was exposed to a strong magnetic field.
A defect occurred in one or two tracks. I n this
case, initialization can be used to take the bad
track (s) out of service and add one or two tracks
from the spare area.
A sector sequence other than the sequence existing
on the disk is desired. See
Initialization Procedures
in this chapter for information on how to specify
the desired sector sequence.
Note:
It is not necessary to reinitialize when a diskette
is to be reused.
\, The purpose of initialization is:
1.
2.
3.
To write identification fields, one for each sector in
all active tracks on a disk.
To write the bad track code in defective tracks. The
maximum permissible number of bad tracks is two.
To write a record in each sector of each active track.
All records are filled with the blank character except
in track 00.
4. To write 80-character records in track 00.
After the index track is written, sectors, 1 through 4 and 6
contain 80 blanks each. Sector 5 contains ERMAP follow-
ed by 75 blank characters. If one or two bad tracks were
specified, the number of the first bad track will be in posi-
tions 7 and 8 of sector 5 with a zero in position 9, the
number of the second bad track will be in positions 11 and
12 of sector 5 with a zero in position 13. Sector 7 contains
VOL 1 in positions 1 through 4, the volume 10 in positions
5 through 10, the sector sequence cO,de is in positions 77
and 78, a W in position 80, and blanks in all remaining
positions of the first 80.
Chapter 8. Disk Initialization
Sector 8 contains the following data set labels:
• HDR 1 in positions 1-4
• DATA in positions 6-9
•
~80
or 128 in positions 25-27 depending on the input
speci fi cati on
• 01001 in positions 29-33
• 73026 in positions 35-39
• 01001 in positions 75-79
• blanks in all other positions
Sectors 9 through 26 contain deleted records with the
following content:
• DO R 1 in positions 1-4
• DATA in positions 6-9
• Sector number in positions 10-11
•
~80
or 128 in positions 25-27
• 74001 in positions 29-33
• 73026 in positions 35-39
• 74001 in positions 75-79
• Blanks in all other positions
As a final step, disk initialization checks the disk to see
that it is written correctly.
Disk Initialization 51