PCMANAGE and DCOMPRES Documentation file

UTILITIES
Vol. 8, No. 21

Ross M. Greenberg
December 12, 1989 (Utilities)

Purpose: To provide automatic compression of infrequently accessed files and
automatic decompression when they are called. The user can set the
inactive period necessary before a file is compressed, can restrict
the drive and/or path of operation, and can specifically exclude
named files or directories.

Format: DCOMPRES [/i] [/An]

Remarks: DCOMPRES is a memory-resident program that should be loaded from an
AUTOEXEC.BAT file. In each subdirectory it creates and maintains a
file called INDEX.CMP. This file stores the date and time each file
was last accessed and whether the file is compressed or not. When a
compressed file is called, DCOMPRES decompresses it automatically.

INDEX.CMP files are normally created with a Read-Only file attribute,
as they should never be deleted while any compressed files remain in
the directory. To remove a directory requires changing this file
attribute with the DOS ATTRIB command (for DOS 3.x) or with a utility
such as ATTR.COM (PC Magazine, June 10, 1986). INDEX.CMP files can be
created with other attributes by loading DCOMPRES with its optional
/An switch, where n has one of the following values: 0 (visible,
read-write); 1 (hidden, read-write); 2 (visible, read-only--the
default); or 3 (hidden, read-only).

If an INDEX.CMP file is accidentally deleted or damaged, all compressed
files in a directory can be restored by loading DCOMPRES with its
optional /i switch parameter and issuing a command such as COPY *.*
NUL.

Format:PCMANAGE [/i] [/dn] [/cn] [/bn] [/pd]

Remarks: When invoked with its default settings, PCMANAGE compresses all files
on drive C: (including those in all subdirectories) that have not been
accessed in 7 days and whose compression will save at least 10 percent
in file length and 2,048 bytes (nominally one cluster). The user can
change the number of days before compression by employing the optional
/dn switch with values from 1 to 32767 for n. Similarly, the optional
/cn switch sets the minimum acceptable compression percentage and
accepts any n value of 5 or greater. The /bn switch sets the number
of bytes in one disk cluster (the minimum real saving possible); it
accepts values from 1024 to 32767 for n.

The optional /pd switch, with an appropriate drive letter (and/or path)
entered for d, allows PCMANAGE to be used on drives other than C: and
permits restricting its operations to the files along a specific path
(and its subdirectories).

The /i switch is used with PCMANAGE when installing the utility. This
should not be done until after you have prepared any necessary
DCOMPRES.EXL (exclude) file, as described in the Notes below. That
done, and with DCOMPRES loaded, use the DOS DATE command to set the
current date back by at least one week. Then enter PCMANAGE /i, which
will cause it to examine all files on drive C: (or as modified by the
/pn switch). Use the DATE command to reset the present date and run
PCMANAGE again, without the /i parameter. All files on the drive
except those excluded by DCOMPRES.EXL or the optional /pn switch will
now be compressed initially, if warranted by the disk space savings.
The files will be decompressed as soon as accessed, and programs called
frequently will not be compressed again.

Running PCMANAGE weekly will automatically cause files that have become
stale-dated to be compressed.

Note 1:Up to 100 files or directories (and child directories below them) can
be excluded from possible compression by PCMANAGE. All OS/2 files and
copy-protected software should be so excluded. To do so, create a
pure ASCII file called DCOMPRES.EXL in the root directory of drive C:.
List one entry per line. To exclude all files that have a .SYS
extension and all files in and under an OS2 directory on drive C:, the
DCOMPRES.EXL file would have two entries:

*.SYS
C:\OS2\*

Note 2:DCOMPRES and PCMANAGE can handle a maximum of 100 files per directory.
Files in excess of this number will not be harmed, but will not be
processed.

Note 3: DCOMPRES should be installed in the AUTOEXEC.BAT file before any
anti-virus software. Anti-virus software that uses checksumming
procedures that cannot be disabled until program execution time is
incompatible with DCOMPRES.