SCANDISK--Notes


Problems fixed by ScanDisk

ScanDisk checks and fixes problems in the following areas of each drive:

*  File allocation table (FAT)

*  File system structure (lost clusters, crosslinked files)

*  Directory tree structure

*  Physical surface of the drive (bad clusters)

In addition, ScanDisk also checks and fixes the following areas of a
DriveSpace or DoubleSpace compressed drive:

*  Volume header (MDBPB)

*  Volume file structure (MDFAT)

*  Ccompression structure

*  Volume signatures

*  MS-DOS boot sector

Types of drives

ScanDisk can find and fix errors on the following types of drives:

*  Hard drives

*  DriveSpace drives

*  DoubleSpace drives (if DoubleSpace is installed)

*  Floppy disk drives

*  RAM drives

*  Memory cards

ScanDisk cannot find or fix errors on the following types of drives:

*  CD-ROM drives

*  Network drives

*  Drives created by using the ASSIGN, SUBST, or JOIN commands

*  Drives created by using INTERLNK

Using ScanDisk when other programs are running

Do not use ScanDisk to repair a drive when other programs are running.
ScanDisk is designed for use when files on a disk are in an unchanging
state. When you are using a file, MS-DOS updates the file allocation table
(FAT) and the directory structure to reflect changes. Such updates are not
always made immediately. If you run ScanDisk when other programs are
running, files might still be open. ScanDisk interprets differences between
the directory structure and the file allocation tables as errors. This can
result in corruption or loss of data.

You cannot use ScanDisk to correct disk errors if you start it from another
program, or when Microsoft Windows or MS-DOS Task Swapper are running.
However, you can check your disk without fixing errors by using the SCANDISK
command with the /CHECKONLY switch. If you run it with Windows, ScanDisk
might detect errors that do not exist when Windows is not running.

Using ScanDisk with PC-DOS 6.1

Do not run ScanDisk on any PC-DOS 6.1 compressed drive. If you do, you will
lose all data on that drive. ScanDisk is compatible only with MS-DOS
compressed drives (DriveSpace drives and DoubleSpace drives) and is not
designed to run on PC-DOS compressed drives.

Using ScanDisk on DoubleSpace Drives

If DoubleSpace is installed (that is, if DBLSPACE.BIN is loaded into
memory), ScanDisk can check and repair DoubleSpace drives and unmounted
DoubleSpace compressed volume files. ScanDisk can also check and repair
DoubleSpace drives and volume files if the DBLSPACE.BIN and DRVSPACE.MR1
files are available. Otherwise, ScanDisk does not work on DoubleSpace drives
or unmounted DoubleSpace compressed volume files. For more information about
the DRVSPACE.MR1 file, see DBLSPACE--Notes. (For more information about
using DoubleSpace with MS-DOS 6.22, see <DBLSPACE>.)

The SCANDISK.INI file

The SCANDISK.INI file is a text file located in the directory that contains
your MS-DOS files. The settings in the [Environment] section of the
SCANDISK.INI file determine certain aspects of ScanDisk's behavior, such as
whether it is configured for a monochrome or color display. The settings in
the [Custom] section determine the default behavior of ScanDisk when you
start it with the /CUSTOM switch.

For more information, read the comments in the SCANDISK.INI file.

Undoing the changes ScanDisk made

If ScanDisk finds errors on your drive, the program gives you the option of
creating an Undo disk, which enables you to undo the changes ScanDisk makes
to your drive. The Undo disk contains information that specifies which drive
it applies to as well as information on every change that ScanDisk made to
that drive.

CAUTION: Use the Undo disk to undo changes only if your drive has not
         changed since that Undo disk was created. If you changed any of
         the files on your drive since you created the Undo disk, do not
         try to undo your changes. If you attempt to use the Undo disk
         after you update a file or directory, or copy or delete a file,
         you might damage your drive structure and lose data.

ScanDisk Errorlevels

When ScanDisk returns to the command prompt, it sets ERRORLEVEL to one of
the following:

0   ScanDisk did not detect any problems on the drive(s) it checked.

1   ScanDisk could not run because the command-line syntax was incorrect.

2   ScanDisk terminated unexpectedly due to an out-of-memory error or an
    internal error.

3   The user chose to exit before ScanDisk had finished.

4   ScanDisk completed all logical checks on all drives, but the user exited
    from one or more surface scans before the scans were complete.
    Errorlevel 4 is not returned if the user chose to bypass the surface
    scans completely.

254
    ScanDisk found disk problems and corrected them all.

255
    ScanDisk found disk problems, but not all problems were corrected.