Hi Ulrich, Mike, others,
The DataPerfect database I developed for the our public Health
Center has been running for 6 years. Doctors and nurses now
asked me to increase the number of computers to 8, and connect
them into a network.
I was very confident that the network would run smoothly because
of a previous experience: for about 3 years computers were
networked in pairs, running 12 hours a day, 5 days a week,
without anyone reporting problems.
Trouble started this week. I networked a pair of computers, just
as I had a few years back, to allow two persons to work
simultaneously and speed up the long process of adding 15,000
new records. It did work, but it turned out to be very fragile.
As soon as the two people use the database more intensively, the
system crashes -- in most cases, both server and client. If on
the other hand they do things slowly, it works just fine.
The hardware is mostly early Pentiums donated to us. The network
software is MS-Client.
Error messages vary. Here are some examples of my collection
(not verbatim, I'm afraid):
From the server:
- "General failure reading drive C"
- LBACache error
- "Disk is write protected"
From the client:
- "Not ready reading drive G"
- (This one is from DataPerfect, in a rare instance when the
client did not crash along with the server:) "Network
error. One or more of the database files can't be accessed
because of the current authorization for the files [..]"
Before writing to you, I wanted to check this with the
DataPerfect discussion group. In their long experience with
concurrent use by many users and even international access over
the internet they never had any issues with networking, except
when the client was trying to cache writes -- which is not my
case, as I only use UIDE or LBACache.
So, that pretty much clears DataPerfect.
The only difference I can think of between the previous networks
that worked well for years and today's is that the former were
used basically by a doctor at the office and his/her assistant
at the reception desk -- a light load on the system -- whereas
this week we tried to use both machines very intensively.
Apparently the computers crash when both users do someting
requiring lots of disk access, typically keeping the
up/down-arrow or PageUp/Down pressed in order to run down a list
of records. As a temporary workaround I wrote "MODE con rate=1
delay=4" (minimum and maximum values respectively) in FDAUTO.BAT
and this indeed prevents crashes if keys are kept pressed, but
if the user taps them quickly the system crashes all the same.
Trying to run a report from the client also crashes the system
as soon as we try to use the database in the server.
The network adapter LED light proved a good indicator of danger.
As long as it is not blinking, we are safe.
We did the tests with 3 different computers at the Health
Center, and I reproduced exactly the same problem with two of my
own computers at home. The cable was replaced too.
I did countless changes of parameters, including the more
obvious such as the "FILES" line, and many others in a
trial-and-error basis, in fdconfig.sys. fdauto.bat,
protocol.ini, and system.ini. The latter two belong to
MS-Client. I tried running with Himemx only (without
jemm386/jemmex) and loading everything low. I also tried about a
dozen different configurations of the Realtek RTL8139 network
adapters. In addition, I tested lower microprocessor speeds like
233 MHz instead of 600 or 800 since it seems that speed is
somehow involved in this.
My "SHARE" line in fdauto.bat is:
loadhigh C:\FDOS\BIN\SHARE.COM /L:40 /F:4096
I mention it because this was one of the things I had to adjust
a few years ago when I first networked pairs of computers. The
default values were not sufficient. Today I tried larger values,
This may or may not be related, but there is at least one
software that will not run properly when SHARE is loaded: the
SuperCalc spreadsheet by Computer Associates, which is otherwise
Of course I have read Ulrich's instructions about DOS networking
and others' too (Jacco, Gerd Röthig), but I do not recall
anything similar to what we are experiencing.
Suggestions will be much appreciated.
PS: Mike, if and when mTCP becomes capable of sharing drives,
I'll probably be among the first "customers" :-)
PS-2: Mike, supposing mTCP can share drives, would that be
sufficient for clients to access the server via the internet?
Marcos Fávero Florence de Barros
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