However, the ADO provider with the fixed name "Oracle.ManagedDataAccess.Client" is not registered in the computer or application configuration file or cannot be loaded, but is not processed in user code.

This is a common error using the Odp.net link ORCL database and requires configuring the system environment variables.

Here's how to fix it:

Locate the following path file: C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config

Note: It's a good idea to back up before modifying ....

Add the following configuration file to the <configSections> node.

<configSections>
    <section name="oracle.unmanageddataaccess.client" type="OracleInternal.Common.CustomSectionHandler, Oracle.DataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
    <section name="oracle.dataaccess.client" type="System.Data.Common.DbProviderConfigurationHandler, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />
    <section name="oracle.manageddataaccess.client" type="OracleInternal.Common.ODPMSectionHandler, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
    ................
    ................
</configSections>

Add the following configuration to the <system.data> node

<system.data>
    <DbProviderFactories>
      <add name="ODP.NET, Unmanaged Driver" invariant="Oracle.DataAccess.Client" description="Oracle Data Provider for .NET, Unmanaged Driver" type="Oracle.DataAccess.Client.OracleClientFactory, Oracle.DataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
      <add name="ODP.NET, Managed Driver" invariant="Oracle.ManagedDataAccess.Client" description="Oracle Data Provider for .NET, Managed Driver" type="Oracle.ManagedDataAccess.Client.OracleClientFactory, Oracle.ManagedDataAccess, Version=4.121.2.0, Culture=neutral, PublicKeyToken=89b483f429c47342" />
    </DbProviderFactories>
 </system.data>

However, the ADO provider with the fixed name "Oracle.ManagedDataAccess.Client" is not registered in the computer or application configuration file or cannot be loaded, but is not processed in user code.