Understanding Oracle database and ODAC installation

Question

I want to use Oracle XE DB in my ASP.NET MVC project. I installed Oracle 11g XE on same machine where is VS running. Installation completed succesfully in C:\oraclexe. Everything as expected, i was able to connect to DB via Server Explorer using default .NET oracle data acces provider. But i want to use ODP.NET, so i installed ODP.NET + ODT in C:\app. Here is first confusing thing. Directory structure of C:\oraclexe..\server and C:\app..\client_1 is similar. Both have NETWORK\ADMIN folder where Tnsnames.ora resides. I understand that client is used to connect to database but:

1. Which Tnsname.ora will be used to connect to database?
2. Oraclexe also contains odp.net folder where Oracle.DataAccess.dll resides. If server installation come with odp.net why i need to install ODAC? Server Explorer in VS offered me ODP.NET drivers for connection only after ODAC install.
3. ODAC comes with Oracle Instant Client. When to use Oracle Client and when Oracle Instant Client? If i decide for Oracle Client and then i will install ODAC for connection, will it also install Instant Client which is part of ODAC?
4. Finally after installation of server and client, VS 2010 still does not offer me Oracle Providers in ASP.NET Configuration

Answer 1

Oracle XE is kinda special in that you typically install the server and client on the same machine. Logically, they are separate, but it does make things a bit harder to understand. For that reason, I will refer to other experts.

1. The folks at ORAFAQ have information about the TNSNAMES.ORA file. My personal strategy is to make all my TNSNAMES.ORA files the same, so there is no opportinity for confusion.

2. ODP.NET is for... .NET use, while ODAC is "native" (OLE) and provides more tools than you may have with just ODP.NET. Use whatever works for your needs.

3. For most cases, you would distribute the Instant Client. The Full Client is more useful for developers. Refer to the documentation and FAQs for details. You can have multiple clients on one machine, so I'm not sure what the problem is.

4. Restart the machine? Did you add the appropriate library/libraries to your environment?