When installing Oracle Data Access Components (ODAC) in a new Oracle Home, Oracle Universal Installer (OUI) automatically copies the Oracle local naming (tnsnames.ora), profile (sqlnet.ora), and directory (ldap.ora) parameter files and settings from an existing Oracle home into the newly installed ODAC home, as long as they share the same bitness. That is, they are both 32-bit installations or they are both 64-bit installations.

Alternatively, existing *.ora files can be copied over from another existing Oracle home, besides the last active one, to the new ODAC Oracle home. OUI provides location information for these files from up to three other existing Oracle homes if they exist. The *.ora files can be customized if the new Oracle home uses a different configuration from the previous Oracle home from which the files were copied over.

If you install into an existing ODAC or RDBMS Oracle home, then no new *.ora files is copied or created.

If you install onto a computer without any previous Oracle homes present, then OUI prompts the user for the database connection alias information. OUI then automatically creates the tnsnames.ora file. If no alias information is provided, then no tnsnames.ora file is created. Even if the user does not have all the database connection information readily available, Oracle recommends inserting placeholder values during the install process, then modifying the tnsnames.ora file later with actual values to replace the placeholders.

ODP.NET tnsnames.ora, sqlnet.ora, and ldap.ora parameter values can be set in a .NET configuration file or within the *.ora file itself. The *.ora file location can be a location different from the standard ORACLE_HOME/network/admin directory. The *.ora settings order of precedence is similar to ODP.NET's settings order of precedence. The main difference is that the *.ora files themselves are included in the search order. The tnsnames.ora and sqlnet.ora precedence order is as follows:

1. app.config or web.config

2. machine.config

3. File location specified by TNS_ADMIN setting

4. The current .EXE or web application root directory

5. %ORACLE_HOME%\network\admin if using ODP.NET, Unmanaged Driver

The ldap.ora precedence order is as follows:

1. app.config or web.config

2. machine.config

3. File location specified by TNS_ADMIN setting in .NET config file

4. File location specified by LDAP_ADMIN setting in .NET config file

5. The current .EXE or web application root directory

6. %ORACLE_HOME%\network\admin if using ODP.NET, Unmanaged Driver

7. %ORACLE_HOME%\ldap\admin if using ODP.NET, Unmanaged Driver

Oracle recommends using an app.config or web.config file to store all these Oracle Client configuration parameter settings.

Once the first tnsnames.ora, sqlnet.ora, and ldap.ora are found and read, no additional *.ora file lower in the precedence order is read. That means all Oracle Client configuration settings must be made in the app.config, web.config, machine.config, or the first set of *.ora files found. Additional parameter values set in *.ora files lower in the precedence order will not be read.

ODAC OUI and xcopy installs ODP.NET with either machine-wide or non-machine-wide configuration for managed and unmanaged ODP.NET. Machine-wide configuration makes global changes to the machine's .NET setup, including placing the provider assembly into the Global Assembly Cache (GAC) and updating the machine.config with configuration section handler and DbProviderFactory information.

Machine-wide configuration also creates a TNS_ADMIN machine.config setting. If TNS_ADMIN already exists as a Windows environment variable in an OUI ODAC installation, then the TNS_ADMIN machine.config setting is set to that directory location. If TNS_ADMIN does not already exist for an OUI ODAC installation, then the machine.config TNS_ADMIN value is set to ORACLE_HOME\network\admin. Xcopy installations always create a machine.config TNS_ADMIN value set to ORACLE_HOME\network\admin.

For ODAC OUI machine-wide configuration installations only, the LDAP_ADMIN setting may also be created in machine.config if an ldap.ora file can be found through the existing LDAP_ADMIN or TNS_ADMIN Windows environment variables. ODAC OUI installations may also create a NAMES.DIRECTORY_PATH setting in machine.config for machine-wide configuration.

If non-machine-wide configuration is selected, then none of these changes are made. Starting with release 12.2, ODAC installs default to non-machine-wide configuration for a new Oracle home installation. For existing Oracle homes, ODAC re-installs the default to the same configuration setting chosen for that Oracle home from the previous installation.

If you plan to install ODAC and the ODP.NET NuGet install on the same machine, then ODP.NET should be configured for non-machine-wide, especially if both share the same ODP.NET version number that .NET Framework uses to distinguish assembly versions, for example, 4.121.2.0.

Users can reconfigure ODP.NET from machine-wide configuration to non-machine-wide configuration by re-installing ODP.NET to the same Oracle home where ODP.NET of the same version is already installed. For example, if you have already configured ODP.NET machine-wide, then you can re-configure it by re-installing ODP.NET onto the same Oracle home and selecting the non-machine-wide configuration option.

For applications that depend on an ODP.NET version that was not configured machine-wide, it is important to note the following:

• ODP.NET assembly or assemblies that the application depends on will need to be copied over to the application directory.

• Proper .NET configuration settings will be required to use Provider Factory, or Provider-specific configuration, or both.