Dec 132017
 
Disck caching in conventional, EMS or extended memory.
File DISCACHE.ZIP from The Programmer’s Corner in
Category HD Utilities
Disck caching in conventional, EMS or extended memory.
File Name File Size Zip Size Zip Type
DISCACHE.DOC 11215 3717 deflated
DISCACHE.EXE 4480 2839 deflated
TPCREAD.ME 199 165 deflated

Download File DISCACHE.ZIP Here

Contents of the DISCACHE.DOC file



























*** DISCACHE V0.01 ***



Hard-disk System Speed-up Utility


For the IBM/PC family and
Compatibles




























(C) Copywrite 1986, WEG Systems.

1


DISCACHE.DOC Version: 0.01


NO WARRANTIES OR GUARANTEES
ARE EXPRESSED OR IMPLIED
WITH THE USE OF THIS PROGRAM
IN ANY ONE ENVIRONMENT

(Any deviation from the instructions supplied below could produce unknown
and possibly undesired results).


Discache works by keeping commonly accessed disk data in memory so that
when such data is read it is copied from memory rather than read from disk.
Three types of memory are supported by DISCACHE:

1. Conventional memory (i.e. PC memory within the normal 640k limit)

2. Extended memory (i.e. AT memory accessed via the standard BIOS INT 15
interface).

3. Expanded memory (i.e. memory accessed via an interface compatible with
the Lotus/Intel EMS).


Contents of the DISCACHE Program Disk
-----------------------------------

This disk contains two files:

DISCACHE.EXE is the disk caching program itself

DISCACHE.DOC is a text file containing these instructions.

Before going any further, you should make a back up copy of the contents of
this disk. You should then use the back up copy for the installation
procedure (described below).


Installing DISCACHE
-------------------

This section describes how to install DISCACHE on a PC.
This involves two steps:


Step 1: Copy DISCACHE.EXE onto the System Disk
--------------------------------------------

You should first copy the file DISCACHE.EXE onto the System Disk used to
boot the PC (or, if on a network server, and the server boots off drive C,
copy the file onto that drive). To do this, you can use the DOS command
COPY or the facilities provided within your network.







(C) Copywrite 1986, WEG Systems

2

Step 2: Specifying DISCACHE parameters
------------------------------------

You should then edit the AUTOEXEC.BAT file on the System Disk, adding a new
line which loads DISCACHE.EXE and which specifies particular caching
parameters.

DISCACHE can take six optional parameters in the command line. These
parameters are described below, together with the syntax you should use.

/M: allocates the specified number of Kbytes of conventional
memory for caching. If using in a network environment you should remember
to leave enough memory to load the network software itself.

/E: allocates the specified number of Kbytes of extended memory
for caching.

/X: allocates the specified number of Kbytes of expanded memory
for caching.

/H: sets the number of hash table entries to the table-size. If
this option is not specified, a suitable default value is calculated.

/P: sets the data prefetch size (in bytes). If you do not
specify a prefetch size, a default value of 2048 bytes is used. The
maximum value you can specify is 16384 bytes.

/D: caches disk accesses to the disk-drive. More than one disk
may be cached by repeating this option.

An example of an AUTOEXEC.BAT file which includes the DISCACHE command line
is given below:

PATH C:\DOS;C:\
PROMPT $P$G
CLOCK.CMD
DISCACHE/M:64/D:C
CLS
MENU1

Configured this way, DISCACHE will allocate 64 Kbytes of conventional
memory for caching on drive C.
Other examples follow:

DISCACHE/M:36/X:2048/D:D
(allows for 36K of conventional memory and 2MB of expanded memory
for caching drive D:)

DISCACHE/X:2048/P:4096/D:C/D:D
(sets up 2MB expanded memory for caching of drives C: & D: using a
prefetch size of 4096K bytes verses the default 2048)

DISCACHE/X:2048/E:1024/P:4096/D:C/D:D
(sets up 2MB of expanded memory and 1MB of extended memory for
caching of drives C: & D: using a prefetch size of 4096K bytes)

DISCACHE/E:1024/P:4096/D:C/D:D
(sets up 1MB of extended memory for caching of drives C: & D: using
a prefetch size of 4096K bytes)


(C) Copywrite 1986, WEG Systems

3

Error Messages:
--------------

This section gives a list of error messages relating to DISCACHE, together
with guidelines on dealing with them.


No cache memory allocated

DISCACHE has not been able to allocate any memory for caching. Check your
system memory configuration settings.


Insufficient table space - caching not enabled

There is not enough space in conventional memory to hold the tables
required by DISCACHE. The table space used increases in proportion to the
amount of memory allocated to caching, so if this error occurs, the amount
of memory allocated to caching must be reduced.

Alternatively, you can increase the prefetch size, as this will cause a
proportional reduction in the table space required.


Invalid disk specified - caching not enabled

** Only a hard disk accessible through the standard BIOS interface is
supported by DISCACHE. ** This error message is displayed if any other
type of disk is specified. Do not specify RAM-disks, or floppy disks.


Invalid command line - caching not enabled

An illegal option has been specified in the DISCACHE command line. Refer to
the command line options section for details of valid options.


Insufficient conventional memory - Kbytes allocated

The amount of conventional memory specified in the command line is more
than there is available. DISCACHE has allocated the maximum amount
available.


Insufficient extended memory - Kbytes allocated

The amount of extended memory specified in the command line is more than
there is available. DISCACHE has allocated the maximum amount available.


Insufficient expanded memory - Kbytes allocated

The amount of expanded memory specified in the command line is more than
there is available. DISCACHE has allocated the maximum amount available.


No extended memory available

Extended memory has been specified in the command line, but none is
available.

(C) Copywrite 1986, WEG Systems

4

No expanded memory available

Expanded memory has been specified in the command line, but none is
available.


Error while accessing expanded memory

DISCACHE has detected a fault while accessing the expanded memory. The most
likely cause of this error is a fault in the expanded memory hardware.


Error reading drive - caching not enabled

DISCACHE has detected a fault while reading the specified disk drive.


Invalid prefetch size for drive - caching not enabled

The prefetch size is not compatible with the disk drive specified. The
prefetch size must be an exact multiple of the sector size of the disk.








































(C) Copywrite 1986, WEG Systems

5

Tips and Such:
-------------

The following tips will help you get the maximum performance from DISCACHE:

* Choose the right application - DISCACHE will slightly degrade disk write-
accesses and therefore any disk which is used predominantly for writing
data may not benefit from disk caching. However in most applications, disk
read activity predominates, and these will perform better with disk
caching. DISCACHE is particularly effective with multi-user database
applications.

* The more memory made available for caching, the more likely it is that
data will be retained in memory. Any mix of the three supported types of
memory may be used, so any spare conventional memory should be allocated
for caching.

* A slight performance improvement may be obtained by increasing the size
of the hash table, using the /H: switch. Each hash table entry requires
two bytes of conventional memory. The default setting is the total size of
cache memory (in bytes) divided by twice the prefetch size.

* Performance may be improved by experimenting with the prefetch size. The
optimal value in most cases will be the cluster size of a disk (ie 2048
bytes for an AT and 4096 bytes for an XT). However, doubling these values
could improve performance under certain circumstances.

* To get maximum performance from a file server, it is recommended that you
should not run any other server or user tasks on that machine.

* File server performance may be improved by increasing the number of
internal DOS buffers. To do this, you specify a BUFFERS= command in the
CONFIG.SYS file. The default value is 3. We suggest that you increase this
to a maximum of 20. Each additional buffer uses 512 bytes of memory.

* It is recommended that DISCACHE using extended memory not be used on PCs
acting as gateway servers.

* DISCACHE will support hard disks that go beyond the 33MB DOS barrier.
However, because most of these hard disks use a DEVICE DRIVER to make all
of the extra space accessable by DOS, DO NOT try to use DISCACHE with any
device driver that splits the larger disk into two or more logical disks.
If you do us it in this type of configuration (i.e. a 60MB disk divided
logicaly into two drives C: & D:) DISCACHE will support the first disk C:
but it will not recognize the second one D:. This is due to the calls for
D: not being routed through the standard BIOS INT 15 that DISCACHE
requires. If your device driver will let you support the ENTIRE disk as
one unit, DISCACHE will support that disk.

** For further information, or if you believe you are having a problem, our
support line can help you 24hrs daily, 7-days weekly. The support line is
operated via the WAFRUG_BBS located in Northern Virginia at: (703)-425-
0695. (300/1200 baud) Using a computer and a modem you can obtain
information or help by calling into our BBS. If the SYSOP is not there to
help you immediately simply leave a message with phone number in the message
area shown as: WEG Systems Mail Support Area and we will get back to you
promptly. -OR-

WRITE TO: WEG Systems
P.O. Box 5072
Springfield, VA 22150
Attn: Eunhee S. Hunter, Pres.

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