Duplicate "oracle.manageddataaccess.client" error while Porting sites from iis 6 to iis 8.5

Hello ,

I am porting the sites ( .NET V4 , asp.net )  from IIS 6 to IIS 8.5. the Site is working on IIS 6 with no issues.

I configured the IIS 8.5 and create a site and have put a simple asp page for testing and it is working fine. Then, I copied the code from IIS 6 , then even the the test asp page is not working anymore and giving the error

HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid.

Config Source:
   22:     </sectionGroup>
   23:     <section name="oracle.manageddataaccess.client" type="OracleInternal.Common.ODPMSectionHandler, Oracle.ManagedDataAccess, Version=4.121.1.0, Culture=neutral, PublicKeyToken=583344535f345345342" />
   24:   </configSections>

moreover I can't even open the authetication icon from IIS, it is giving the error message : There is duplicate "oracle.manageddataaccess.client" section defined.

I am sure that code is okay as it is working on IIS 6

any idea as to why this behaviour occurs is  is greatly appreciated as I am having this error most time and it is annoying.

F.