Dotnetnuke migration from SQL 2005 to SQL 2012

I'm trying to upgrade my DNN v6 from a SQL Server 2005 to a SQL Server 2012. My problem is, after modifying the web.config to match the new appSettings, my website automaticaly runs the install wizard. My IIS was running on a 2003 server and is now on a 2012 server.

Is it a necessary step to install a new instance of DNN?

Thanks for your help