16-bit DOS application file locking problem

[Kevin Myer]

Hello,

If someone has a pretty good memory, they might remember that I posted
about an apparently file locking problem I was having with our library
automation system over the summer.  I think that I can provide a little
more detail at this point and hopefuly someone will have some fresh
insights.

The problem:  trying to use a multiuser library system which ran under DOS
(and is now running in a "DOS" shell under Windows NT 4.0).  Access
control is created by having two different users - Circulation and Patron.
Circulation has full control, Patron only has access to a Card Catalog
section and read access to the database directory.  However, it appears
that certain activities trigger some sort of lock on certain files,
effectively rendering a multiuser application to be only single user.  For
example, 8 workstations are logged in as Patron and are searching the card
catalog.  Circulation logs into the main circulation computer and starts
cataloging.  All the other users get bumped off with errors about not
being able to access the database or "Index positioning no longer
current".

My original problem was being unable to use the system at all with more
than one machine at a time because not more than one machine could get at
a certain semaphore file at a time.  I found a work around by adding:

        fake oplocks = yes
        veto oplock files = /*.SEM/

to that volumes configuration in my smb.conf.

As far as I know, I have duplicated file permissions on my Linux box as
close as possible to what they were when the volume was hosted off a
Windows NT box.  So it would seem to me that Linux has some sort of
different locking mechanism for files than NT did and that is preventing
certain functions of our library system from working the way they used to.
Documentation seems to indicate that certain locking features are missing
in x86 Linux versions of Samba.  

Ideally, I'd love to dump this 16-bit DOS version of the library software
and go to a Windows version but that won't happen for at least another
year and the librarians are getting antsy to be able to fully use the
system like they used to be able to.  Guess I should have tested the setup
a little more thoroughly before declaring it production ready ;)

By the way, for what its worth:

RedHat Linux 5.2 with kernel 2.2.10 with software RAID5
Dual Pentium II 300Mhz
512Mb RAM
10/100 Ethernet

If anyone can enlightenment on file locking, ala Samba, or point me to
documentation, I'd really appreciate it.

Thanks,

Kevin

-- 
     ~        Kevin M. Myer
    . .       Network/System Administrator
    /V\       ELANCO School District
   // \
  /(   )\
   ^`~'^