While connecting Opkey with the Oracle database, located on local or remote machine, Opkey users come across such issues:
System.Configuration.ConfigurationErrorsException: An error occurred creating the configuration section handler for system.data: Column 'InvariantName' is constrained to be unique. Value 'Oracle.DataAccess.Client' is already present.
The most common cause of such type of issue is installing or uninstalling of ODAC driver multiple times.
Resolution: The resolution for the above cause is to remove one row from the machine.config file of Microsoft.Net folder.
The machine.config file can be found at the following path: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config
The row to be deleted is given below:
"<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=18.104.22.168, Culture=neutral, PublicKeyToken=89b483f429c47342" />
Check before row deletion: Please check that the row with the above given value exists twice in the machine.config file. Now remove the last row with these values.
Radhe Shyam Prajapati