Hello,

Platform:     Windows NT WorkStation 4.0, Service Pack 2
Language:     Visual Basic 5 Enterprise, Visual Studio Service Pack 1

I've succeeded in writing a multithreaded ole server using the
CreateThread Win32 API call. I've been tracing the progress of my
application by writing position marking messages to a log file. The
threads run (I can see the main thread ID, and up to three others,
depending on what I am doing). The problem I am encountering is that I
get a GPF as soon as I do anything having to do with the DAO within my
thread. This GPF does not occur immediately, since I get a fair amount
of messages from my other threads before the GPF occurs.

I'm compiling to Native Code, Optimizing for speed. The server is an
ActiveX EXE, with no visible interface. Unattended execution is enabled.
It's using a thread pool of 1 thread. The reason I am using CreateThread
instead of using the threading built into VB (Sincle Thread Per Object
or a Thread Pool) is because I need to be able to share global data
among the threads.

I've looked in the Help, Books OnLine, Knowledge Base. I've called
Microsoft Technical Support, but since MultiThreading is not officially
supported by VB, they can't really help me much at this time. They have
suggested using RDO (to see if it's just the JET Engine) instead, but I
would prefer to avoid this for the moment, as I haven't used the RDO
before, and, at present time doesn't permit a learning curve, especially
for something that might not work.

Thanks In Advance

N Varacalli

--
The views expressed herein do not represent the views of my employer.

The Address in the header is mangled, delete appropriately.

To reach me via e-mail, try
NICHOLAS_VARACALLI at non-hp-Canada-om1.om.hp.com

Just a note: if you're accessing globals from both threads, you'll want to
look into the various synchronization APIs to make sure your threads don't
stomp on each other. MSDN has lots of articles on the theory, MSJ has some
examples of their use in VB5 in the last 2 issues (August and September).

Actually, it's my understanding that DAO isn't thread-safe (I believe the
ASP documentation mentions this somewhere). ADO is thread-safe; I'm not
sure about RDO.

-Jon

One should probably consider using Critical Sections.
Do you happen to know if there are any VB samples for that? It seems to be
quite trivial
but I havn't tried it yet.

Alon

VB doesnot allow you to create multithreads.
Better create an out of process OLE server and use OLE automation.
(stollen from Appleman's book)

Of course,the problems might be that DAO is not reentry -- i.e., does not
support multi-tasking.  Does anyone know for sure?

Richard L Rosenheim

N Varacalli
--
The views expressed herein do not represent the views of my employer.

The Address in the header is mangled, delete appropriately.

To reach me via e-mail, try
NICHOLAS_VARACALLI at non-hp-Canada-om1.om.hp.com

Check the last 2 Microsoft Journals. I used the CriticaSection class
provided.

Thanks. I will.
--

-------------------------------------
Alon Fleischer
Hilonet Israel Ltd.
8 Tarpab St. Ramat Gan 52110 Israel
Tel: +972-3-6135068   Fax: +972-3-6136718


HTTP:  http://hilonet.com
-------------------------------------

Multithreading DOES work in VB...you will just have to put up with the
GPF's.  No way around it.  Trust me, I've been in touch with MS about
this for a while.  Try it yourself :)

On Fri, 01 Aug 1997 13:56:21 -0400, NV

Followup:

According to some helpful souls in these newsgroups, and some strong
hints from Microsoft Tech Support, it seems that DAO is not threadsafe.
I'm currently investigating ADO, RDO, and binary files as alternatives.
If anyone has any other suggestions, or wants me to keep them posted,
please e-mail me.

Thanks for the help.

N Varacalli
--
The views expressed herein do not represent the views of my employer.

The Address in the header is mangled, delete appropriately.

To reach me via e-mail, try
NICHOLAS_VARACALLI at non-hp-Canada-om1.om.hp.com

It works nice, and shocked a few people! 8-)

Steve

Steve