Replying to Database System

Even though I don't understand the question, but talking about scope, I can say that most DBMS work separately from the OS, for example if you have a circle of OS, then in that circle you would have another smaller circle of a DBMS which is separate.

Microsoft SQL Server and other Microsoft products seems to integrate OS functions into their DBMS, because you're able to use dot.NET from the DBMS and take control of some OS functions, you can use C#, visual basic and etc. which is something really great, the scope of Microsoft DBMS gets bigger and an interface is not needed which can integrate two different scopes.

Oracle DBMS doesn't use this technique, but I believe they're going into that direction in one or another way by using their own hardware and controlling all the layers from hardware, middleware and applications.

So talking about enterprises and interfaces, maybe this is the issue?

Can you please be more precise while asking this? What are you talking about?
Looks like a question your teacher asks you in order to se if you were sleeping during last course, isn't it?
More precisely, the DBMS is the database system, or what were you talking about?

The DBMS acts as an interface between what two components of an enterprise-class database system?