Re: Help! Multithreaded app needs to access Oracle

  Oracle Call Interface is really thread-safe in 7.3. But you can't access Oracle from different threads on one connection, only one thread per connection may be running at a time, but one process may have as many connections to Oracle as needed. All is tested on Windows NT.

Regards, Victor Poteryahin.

John Verbil <jverbil_at_netmail.mnet.uswest.com> wrote in article <32BB09DE.BA2_at_netmail.mnet.uswest.com>...
> Matthew K. Smith wrote:
> >
> > I'm having a problem accessing our Oracle 7 database from two different
> > threads within a C++ application. What happens is that each thread
 tries
> > to
> > access the database at the same time and the app crashes, giving me the
> > following message:
> >
> > ORA-03106: fatal two-task communication protocol error
> >
> > To my knowledge, Oracle will not allow a single process to have
 multiple
> > connections to it, so I know that is not the solution.
> >
> > It was also suggested that I use PL/SQL scripts that reside on the
 database
> > instead of embedded SQL in my app. Unfortunately that will not work
 either
> > because the tables being accessed by my app are constantly changing,
 and
> > PL/SQL scripts would have to be re-written all the time.
> >
> > For the time being, I have defined a mutex lock that will not allow the
 two
> > threads to access the database at the same time, but this does not
 allow
> > the app to achieve the speed that we need. If any of you have
 encountered
> > similar problems, or know of a solution, I would appreciate your
> > suggestions.
>
> Oracle libraries are not thread-safe prior to 7.3; we have yet to
> install 7.3 here so I haven't yet verified the rumour that 7.3 is
> thread-safe. In my client-server app in a 7.2 installation, we have
> multiple single-threaded server processes each with their own connection
> to Oracle. My multithreaded client can then issue many RPCs
> simultaneously, each of which is distributed to a separate server
> process.
>
> If you're already on 7.3, I'm not sure I can be too much help, but check
> your TWO_TASK environment variable. If the program you're executing is
> on the same machine as the database itself, use the pipe driver "P:",
> not the TCP driver "T:". Besides the pipe driver being faster, we had
> some strange problems (I can't recall specifically, it's been too long)
> with the TCP driver when we first set up our servers.
>
> If you're pre-7.3 and are in a client-server environment, I'd recommend
> the client-server approach above to solve your problem; it works quite
> well here - from the client's perspective, we have multithreaded access
> to Oracle.
>
> If you don't have a client-server framework to build from, I think
> you're stuck with the mutex until you get 7.3.
>
> Let me know if this helps, especially if you're on 7.3 - we plan on
> converting 2Q97 and I'm anxious to hear how thread-safe 7.3 really is.
>
> --
> John Verbil
> U S WEST Communications
> Information Technologies
> jverbil_at_uswest.com
> (303) 896-0916
>
Received on Mon Dec 23 1996 - 00:00:00 CST