Using both Oracle Client 32 and 64 in same machine

1. Install Oracle x64 Client (I used 12c 64 bit version)
I selected Administrator bacause i wanted to use admin tools from this version

(http://www.oracle.com/technetwork/database/enterprise-edition/downloads/database12c-win64-download-2297732.html)

2. Install 32 bit version of Oracle client. This time select Instant client we need only client. I installed Oracle client 11 32 bit version.

3. now both versions are installed. default installation folders will be as follows.

Client x32

C:\app\{username}\product\11.2.0

Client 64

C:\app\client\{username}\product\12.1.0

4. Now we need to create a logic to use 32 or 64 based on the application.

C:\app\client\{username}\product\12.1.0

Create symbolic link using following commands. (Note: run command prompt with administrator)

For 64 bit version

mklink /d  c:\windows\system32\orax C:\app\client\{username}\product\12.1.0\client_1\bin

For 32 bit version

mklink /d  c:\windows\syswow64\orax C:\app\{username}\product\11.2.0\client_32

5. Finally set the path environment variable. add c:\windows\system32\orax to existing path variable. and remove any other paths added with Oracle 12 and 11 client installation.

Ex: Final path will be as follows.

c:\windows\system32\orax;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\S

Restart all visual studio instances and run again.