I started bellowing discussion inappropriate place. So I am repeating it again here.
I created a web application (VS 2010, NET 4.0) aiming to implement an OracleMembershipProvider. Using "Oracle Database 2 Day + .NET Developer’s Guide 11g" guide, I installed and pointed to my oracle database. An user was also created checking the OracleMembershipProvider inside Provide tab of ASP.NET configuration and I am able to log in fine using web forms authentication. But, when I check an ORA_ASPNET_USERS table, it was empty and revealed that my login page was connected to an embedded MsSQL database, however, I set the OracleMembershipProvider as default one in web.config.