12c: Where does the DB reference a SQLNET.ORA when GRID and RDBMS are present?

In both RAC and standalone installations where both an RDBMS_HOME and GRID_HOME are present, the database will reference a sqlnet.ora file in its own home.  In other words, for any sqlnet.ora file changes that are to impact the database (including Oracle Net tracing, DCD, etc), the sqlnet.ora file that should be edited would be located in:   RDBMS_HOME/network/admin

Obviously, this would not be the case if a $TNS_ADMIN variable is set in the database's environment AND it points to a different directory.  We can verify this using the following LSNRCTL commands:

LSNRCTL>set current_listener <listener name here>