I seem to be having an issue connecting a 32-bit .NET application to a 64-bit server, without a full Oracle client.

If I build a 64-bit application, using the 64-bit ODP.NET dll's or a 64-bit instant client, everything seems to work fine. But if I build a 32-bit ODP.NET application or use the 32-bit instant client, it always goes "looking" for the 64-bit dll's, and errors out on me.

Has anyone encountered this before, or have any suggestions as to what issues we might be having?

We don't have the same problem connecting to SQL Server (of course, SQL server uses mixed-mode assemblies...)

  • Are the client and server on the same machine? Whether the server is 32 or 64 bit should make no difference to the client AFAIK Commented Oct 13, 2011 at 10:45
  • To the client it doesn't. To the actual dlls it seems to. Commented Oct 13, 2011 at 10:50
  • The dlls on the client or the server? Commented Oct 13, 2011 at 11:00
  • No, this is a .NET assembly that's being built. The .NET assembly looks for the ODP.NET 64-bit dll, regardless if you you're running 32-bit, or 64-bit. This obviously causes us problems on 32-bit systems. The problem goes away if I use the full oracle client, or if we deploy to a 64-bit machine. Theoretically...it doesn't make any sense. Commented Oct 13, 2011 at 12:46
  • I think I understand. The fact that the server is 64-bit is not the issue right? Rather there is some incompatibility between different bits on the client? Commented Oct 13, 2011 at 13:32

1 Answer 1


Did you control PATH Environment Variable to which comes first, 32 or 64. Which ever client is installed last, change PATH accordingly. I have encountered similar issue. Windows uses PATH environment variable to decide which dlls to load. I have two clients installed in my machine and used PATH variable to force which one to use.

 Directory of C:\oracle\product\11.2.0

20.09.2011  10:07    <DIR>          .
20.09.2011  10:07    <DIR>          ..
20.09.2011  10:08    <DIR>          client32Bit
20.09.2011  10:04    <DIR>          client64Bit

C:\oracle\product\11.2.0>echo %PATH%

  • Welcome to dba.se Atilla and thanks for your useful contributions here and elsewhere :) Commented Nov 14, 2011 at 11:19
  • Thanks for the contribution, sorry I didn't get back to you earlier, had a baby and a bit of a hiatus from this project. However, changing the path hasn't resolved the issue. Thanks for the info though and welcome to stack exchange! Commented Nov 21, 2011 at 22:38
  • @BrianDeragon congratulation on having a baby. Commented Nov 22, 2011 at 8:10

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