9.0 ERROR DETECTION AND CORRECTION
9.1
Write Error
If
an
error occurs during a write operation, it will
be
detected
on
the next revolution by doing a read opera-
tion, commonly called a
"write
check."
To
correct the error, another write and write check operation must
be
done. If the write operation is not successful after ten attempts have been made, a read operation should
be
attempted
on
another track to determine if the media or the drive is failing, If
theenor
still persists, the
disk should
be
considered defective and discarded.
9.2 Read Error
Most errors that occur will
be
"soft"
errors; that
is,
by performing
an
error recovery procedure the datawill
be
recovered.
Soft errors are usually caused
by:
1.
Airborne. contaminants that pass between the read/write head and the disk. These comtaminants will
generally
be
removed by the cartridge self-cleaning wiper.
2.
Random electrical noise which usually lasts for a few
p.sec.
3.
Small defects
in
the written data and/or track not detected during the write operation which may cause a
soft error during a read.
The
following procedures are recommended to recover from the above mentioned soft errors;
1.
Reread the track ten times or until such time
as
the data is recovered.
2.
If data
is
not recovered after using step
1,
access the head to the adjacent track
in
the same direction
previously moved, then return to the desired track.
3.
Repeat step 1.
4.
If data is not recovered, the error
is
not recoverable.
40
To Next Page
