i had previously installed Oracle client 10g on win 2003 machine to connect to my Oracle db from my .NET app.

this time i wanted to do the same from my Win Server 2008 R2 x64 machine…
for 64 bit machines Oracle has released a 11g 64 bit client which you can get from here:
http://www.oracle.com/technetwork/database/enterprise-edition/downloads/112010-win64soft-094461.html
(win64_11gR2_client.zip).

Run the installation and select the first item (Oracle instance client):

Continue the installation…it will finish in no time.

However, after installation there was no tnsnames.ora and sqlnet.ora files…and there was no Network and Admin folders. In all previous installations these were the folders/files i deal with to set my settings and service names.

What i did next was wierd but worked! i manually created folder Network and inside it created folder Admin…the full path was:
C:\app\username\product\11.2.0\client_1\Network\Admin
And i created the tnsnames.ora and sqlnet.ora inside the above path.
That did the trick.

Before that…

If you are going to invoke Oracle client from a .NET application like me, you will get an error that says:
“Attempt to load Oracle client libraries threw BadImageFormatException. This problem will occur when running in 64 bit mode with the 32 bit Oracle client components installed.”
if your application process is targetting 32-bit.

if you are using a console application, go to project properties –> advanced compilation options and change the target cpu to x64.
From IIS 7 make sure that the setting for the application pool accessing Oracle has “Enable 32 bit applications” set to false.

PS: i read that its an IIS 7 best practice to keep 32-bit processes (pools) working on x64 machines. so the above step might incur performance overhead. my next attempt will be to install Oracle client 32-bit on my x64 machine and see if that works…