Epson 386SX - Manual (Page 235)

The formatting options work as follows:
Format
first scans the disk (if it has no defective track
table) for defective (bad) tracks and lets you decide which
tracks to mark as bad. Then the program formats the disk
and marks those bad tracks so they are never used to store
data.
Destructive surface analysis
tests the
entire disk for read/write errors or unflagged bad tracks and
updates the defective track table. Because this option writes
and reads data on the disk, it destroys all data on any track
that produces an error. You cannot run the Destructive
surface analysis on a disk that has never been formatted.
Non-destructive surface analysis
checks
the disk for unflagged bad tracks without destroying data.
You cannot run the Non-destructive surface analysis on a
disk that has never been formatted.
The type of format you choose depends on whether you are
reformatting a disk that has been used or formatting a new disk
for the first time. See the recommendations below.
Reformatting a Used Disk
If you are reformatting a disk you have been using that appears
to be damaged, follow these steps:
1. Use the Non-destructive surface analysis test to check for
unflagged bad tracks.
2. If errors occur during the Non-destructive analysis, use
BACKUP to back up the data on your disk. (See your
MS-DOS Reference Manual for instructions on how to use
BACKUP.)
3. Run the Destructive surface analysis.
Physically Formatting a Hard Disk D-3