I was having trouble getting my OBIEE 12c repository to connect to my Oracle database via a TNS name.  I had recently deinstalled the Admintool, and upon reinstallation it wasn't able to use a TNS entry to connect to the database in a connection pool.  I put on my detective hat and figured out where the tool was expecting to find TNSNAMES.ORA.  I thought I should share that process and save others the trouble  These steps apply specifically to Windows.

The file I run to open the Admin tool is located (in my system) at C:\obiee_12c_admin\domains\bi\bitools\bin\admintool.cmd

That file contains this single line: call %~dp0\..\..\..\..\bi\bitools\bin\admintool.cmd

Each of the 4 occurrences of ..\ goes up the path one level from the location of the file in which this command is running.  So, that means that I'm going up the chain four levels, knocking off bin, bitools, bi, and domains, coming to rest on c:\obiee_12c_admin.

Then the command adds \bi\bitools\bin.  So, at this point, the command will run c:\obiee_12c_admin\bi\bitools\bin\admintool.cmd

Let's examine that command file.  It  contains these important lines:

set CLIENT_HOME=%~dp0\..\..  which means to go up two levels from the current file, which would leave us at c:\obiee_12c_admin\bi

set DOMAIN_HOME=%CLIENT_HOME%\..\domains\bi   which strips one level (bi) from client_home, then adds \domains\bi.  So DOMAIN_HOME is c:\obiee_12c_admin\domains\bi

CALL %CLIENT_HOME%\bifoundation\server\bin\nqinit.cmd %*    which translates to c:\obiee_12c_admin\bi\bifoundation\server\bin\nqinit.cmd

That file contains these key lines:

set ORACLE_BI_ENVIRONMENT_DIR=%DOMAIN_HOME%\config\fmwconfig\bienv  which translates to c:\obiee_12c_admin\domains\bi\config\fmwconfig\bienv

set TNS_ADMIN=%ORACLE_BI_ENVIRONMENT_DIR%\core  which translates to c:\obiee_12c_admin\domains\bi\config\fmwconfig\bienv\core

So, it appears that the OBIEE Admin Tool is expecting to find TNSNAMES.ORA in c:\obiee_12c_admin\domains\bi\config\fmwconfig\bienv\core

Checking that directory, I see that the only file there is bi-environment.xml. 

After I pasted the contents of my regular ..\network\admin directory (which contains the .ora files for my database) into c:\obiee_12c_admin\domains\bi\config\fmwconfig\bienv\core, the Admin Tool connected correctly.