DOCUMENT:Q96386 26-NOV-1999 [msdos] TITLE :Cannot Lower Estimated Compression Ratio with DoubleSpace PRODUCT :Microsoft Disk Operating System PROD/VER:MS-DOS:6.0,6.2,6.22 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft MS-DOS operating system versions 6.0, 6.2, 6.22 ------------------------------------------------------------------------------- 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: 1. 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" (without the quotation marks) 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 2. 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" (without the quotation marks) 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. 3. 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" (without the quotation marks) 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. Additional query words: 6.00 6.20 double space drive ====================================================================== Keywords : Technology : kbMSDOSSearch kbMSDOS622 kbMSDOS620 kbMSDOS600 Version : MS-DOS:6.0,6.2,6.22 ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 1999.