DBase File locking issues

Jim Morris Jim at Morris.net
Thu Sep 16 13:21:48 GMT 1999

Hello Matthew,

Wednesday, September 15, 1999, 8:08:29 PM, you wrote:

Vanecek> Are you sure it's not a problem rather with the DBase engine failing to
Vanecek> lock the records properly, for whatever reason?  That's how FoxPro
Vanecek> works, anyhow, where the files live on a Novell share, and FoxPro isn't
Vanecek> all that different from DBase (or, didn't used to be, anyhow).

Well, I am pretty darned sure at this point it isn't the DBase engine
failing, since multiple DBase engines have been used now. I've written
Win32 console and GUI apps using both CodeBase and the Borland
Database Engine (BDE), and DOS apps using CodeBase.

Furthermore, since the posting, I've written test Win32 test apps using
the Borland Database Engine (BDE) using C++ Builder 4.  Two clients
appending records to the same file on the Samba server using the BDE
test app have dramatic results.  Entire blocks of records from each
client can be missing when you go back to check the file - yet no
errors were returned during the test run.  The original test
application was a DOS app, comiled with CodeBase 5.1 - a commercial C
library for DBase access that we've been using in production
environments for years, with multiple PC's talking to a file server.

I think thought the critical fact comes down to this:  the problem
does not occur using Windows NT Server 4.0 on the fileserver.  These
DOS apps at least have been running off either an OS/2 or NT
fileserver for the past 6 to 8 years.  Anyway, yesterday, I made space
on my Linux (Redhat 6) fileserver here at my home office, and
installed a copy of Windows NT Server 4.0.  No data loss occurs.

Another thing to reiterate from my original post - this is a problem
that seems to occur only when multiple PC's are WRITING records to the
DBase file at the same time. If one client is appending records, while
another just reads records, everything works file. If I run 2 copies
of the client on the same PC, both appending records as fast as they
can, everything is fine.  OF course, on a uniprocessor Win98 system,
those two copies of the program are never going to append at the exact
same instant.

I intend to so some further testing here this morning - I'm going to
boot my Dual-boot Caldera OpenLinux 2.2 / Win98 system up into Linux,
and install Samba 2.0.5a here from the tar ball, and see if the same
issue occurs with OpenLinux 2.2, or if its just a Redhat 6.0 problem.
Both Linux servers I've tested on so far were running Redhat 6.0.  And
FYI, those Redhat 6.0 systems are on different LAN's, in different
states - so I can pretty confidently say this isn't tied to a
networking problem.

| Jim Morris  | Business:  jmorris at rtc-group.com |
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