Cannot Lower Estimated Compression Ratio with DoubleSpace (96386)
The information in this article applies to:
• Microsoft MS-DOS operating system 6.0
• Microsoft MS-DOS operating system 6.2
• Microsoft MS-DOS operating system 6.22
This article was previously published under Q96386
This information applies to both Microsoft DoubleSpace and Microsoft
DriveSpace. For MS-DOS 6.22, use DRVSPACE in place of DBLSPACE for commands
and filenames.
SYMPTOMS
DoubleSpace doesn't allow you to lower the estimated compression ratio
(ECR).
CAUSE
When you lower the ECR, you effectively reduce the size of the compressed
drive. Reducing the size of the compressed drive requires reducing the size
of the file allocation table (FAT). If there is an entry in use near the
end of the FAT, DoubleSpace cannot reduce the size (lower the ECR).
The following are examples of conditions that can prevent DoubleSpace from
lowering the ECR:
• Lost allocation units at the end of the compressed drive
• Heavily fragmented files on the compressed drive
• A file (with Hidden and/or System attributes set) stored at the end of
the compressed drive
WORKAROUND
To correct the lost allocation unit problem, run ScanDisk on the compressed
drive (if you are using MS-DOS 6.0, run CHKDSK /F).
To correct the fragmented drive problem, run DEFRAG /F /H on the compressed
drive.
To correct the hidden-system file problem:
• Use the DIR command to search for system files on the compressed drive.
For example, if your compressed drive is drive C, type dir c /s /as /p at the MS-DOS command prompt and then
press ENTER. Make note of the files that are listed.
The following chart lists programs that are known to write system
files at the end of a drive:
Program name Program filename System file created
-----------------------------------------------------------------------
Microsoft MS-DOS Mirror MIRROR.COM MIRORSAV.FIL
Central Point Mirror MIRROR.COM MIRORSAV.FIL
Symantec Norton Image IMAGE.EXE IMAGE.IDX
Symantec Norton Format Recover FR.EXE FRECOVER.IDX
Microsoft MS-DOS 5.0 Undelete MIRROR.COM PCTRACKR.DEL
Microsoft MS-DOS 6.0/6.2 Undelete
- Delete Tracker UNDELETE.EXE PCTRACKR.DEL
- Delete Sentry UNDELETE.EXE CONTROL.FIL
Central Point Undelete
- Delete Tracker UNDELETE.EXE PCTRACKR.DEL
- Delete Sentry UNDELETE.EXE CONTROL.FIL
• Use ATTRIB to remove the file attributes on the system files you found
in step 1. For example, if you have a Mirror file on drive C, type the
following at the MS-DOS command prompt and then press ENTER:
attrib -r -s -h c:\mirorsav.fil
NOTE: If the system files you found are used by a delete-tracking
program (refer to the table in step 1), you need to reboot your computer
without loading the corresponding program file before you change the
file attributes on the system file. To do so, reboot your computer and
press F5 when the "Starting MS-DOS..." prompt is displayed.
• Run Microsoft Defragmenter on the compressed drive. Change to the
compressed drive and type "defrag /f /h" (without the quotation marks)
at the MS-DOS command prompt.
You should now be able to lower the ECR on the DoubleSpace-compressed
drive.
If you were able to successfully lower the ECR on the compressed drive,
reset the file attributes on the system file addressed in step 2. For
example, type the following at the MS-DOS command prompt and then press
ENTER:
attrib +r +s +h c:\mirorsav.fil
NOTE: The DoubleSpace ECR is not based solely on the expected
compressibility of new data; it is also dependent on the size of the
compressed volume file (CVF). You may need to resize the compressed drive
to change the ECR to the desired value.
| Modification Type: |
Major |
Last Reviewed: |
11/26/1999 |
| Keywords: |
KB96386 |
|