Automating RAMDrive Compression with DoubleSpace (95633)
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 6.21
• Microsoft MS-DOS operating system 6.22
This article was previously published under Q95633
This information applies to both Microsoft DoubleSpace and Microsoft
DriveSpace. For MS-DOS 6.22, use DRVSPACE in place of DBLSPACE for commands
It is possible to compress a RAM drive with DoubleSpace. However, since the
information on the RAM drive is lost each time you restart your computer,
you must recompress the RAM drive each time you start your system.
You can avoid this problem by storing the RAM drive compressed volume file
(CVF) on your hard disk drive and placing two commands in your AUTOEXEC.BAT
file to copy and mount the CVF on the RAM drive when you start your
You can automate the compression of the RAM drive with the following
• Create RAM drive. For example, to create a 1-megabyte (MB) RAM drive in
extended memory, place the following statement in your CONFIG.SYS file:
device=c:\dos\ramdrive.sys 1280 /e
• Restart your computer to load the RAM drive.
NOTE: MS-DOS assigns the next available drive letter for the RAM drive.
For example, if you only have one hard disk drive (C), the RAM drive is
assigned the drive letter D. This procedure uses drive D as the RAM
• Compress the RAM drive. For example, to compress drive D, type the
following at the MS-DOS command prompt and the press ENTER:
• Resize the compressed drive to its maximum size (and thereby reduce the
size of the host drive to zero bytes). For example, type the following
at the MS-DOS command prompt and then press ENTER:
dblspace /size /reserve=0 d:
• Change the CVF attributes so the file can be copied. For example:
attrib h:\dblspace.000 -s -h -r
This example assumes the host drive is drive H. To determine your host
drive, type dblspace /list at the MS-DOS
command prompt. Write the drive mapping information down, because you
need it in step 5.
• Copy the compressed volume file (CVF) to your hard disk drive.
To avoid having to recompress the RAM drive each time you start your
computer, you must store the CVF on your hard disk drive. This requires
approximately 1 MB of space.
To copy the compressed volume file to your hard drive, type the
following at the MS-DOS command prompt:
Since this file cannot be compressed (it already is), you should copy it
to an uncompressed drive.
copy h:\dblspace.000 c:\dos\ramcvf.000
• Add the following lines to your AUTOEXEC.BAT file so that the CVF is
copied to your RAM drive and mounted each time you start your computer.
Substitute the appropriate drive letters for C, D, and H. Drive C should
be the uncompressed drive on which you store the RAM drive CVF; drive D
is the RAM drive, and drive H is the host drive.
REM Copies and Mounts CVF to RAM drive
copy c:\dos\ramcvf.000 d:\dblspace.000
dblspace /mount=000 d: /newdrive=h:
• Restart your computer. To determine if the procedure worked, type
dblspace /list at the MS-DOS command
prompt and press ENTER.
WARNING: Any information stored on a RAM drive is lost when you restart or
turn off your computer. To prevent data loss, copy any file you want to
save from your RAM drive to your hard disk drive before turning off your
NOTE: Since DoubleSpace uses a 512-byte sector size, RAM drives must be
created with a 512-byte sector size so that DoubleSpace can compress the
drive. If a RAM drive is created with a sector size of 128 bytes or 256
bytes, DoubleSpace does not recognize the drive as available for
compression. The default value for the sector size of a RAM drive created
with RAMDRIVE.SYS included with MS-DOS 6.0 is 512 bytes. For information on
changing the sector size of a RAM drive, type the following at the MS-DOS
command prompt and press ENTER:
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