Thanks for looking into this Gonzalo, I'm not sure what you mean by "which model i'm using?" I don't have to fill in anything. Once user is in registration screen all they do is, select the available course and hit Register button in order to get enrolled into a course. Do you think i can use Optimistic or Pessmestic lock on the database in this regard, Let me know. Also I'm not sure about the models so let me know what kind of models are available.