I am sure others out there where like me.  New kid on the block Windows 7 x64 installed, Oracle 11g x64 installed on Server 2008 R2, time to test the .NET web application in full x64 mode.  Setup my target test server with the Oracle 11g x64 client, install the software and to my amaze everything major works.  Go to my development machine and started to setup the Oracle database to Visual Studio.  Nothing, get an error that Visual Studio cannot connect.   After some investigating, I realize that Visual Studio 2008 and 2010 Beta 2 are still compiled in 32 bit.  Was not shocked that this was an issue for 2008, I still only have it installed because of a DB2 issue with 2010.

So to connect your Visual Studio environment to Oracle you need to do the follow:

• Install the Oracle Client x64 (for applications that are 64 bit)
  • I usually install this into client_1
• Install Oracle Client x32
  • I usually install this into client_2
• Setup the ‘Local net Service Name’ either by using the Net Configuration Utility or updating TNSnames.ora manually for both client_1 and client_2.

If you are running Windows 7 x64 you might also experience the following error when setting this up:

“ORA-12638: Credential retrieval failed”

To solve this edit \client_x\network\admin\sqlnet.ora

“SQLNET.AUTHENTICATION_SERVICES= (NTS)”

To:

SQLNET.AUTHENTICATION_SERVICES= (NONE).”

If the above does not work try:

SQLNET.AUTHENTICATION_SERVICES= (BEQ,NONE)