DBMS architecture describes the structure and how the users are connected to a specific database system.
Architecture affects the performance of the database.
In the single-tier architecture, all the components of the DBMS reside on a single server.
It is the most straightforward approach.
The two-tier DB architecture allows the client to communicate directly with the database- thus making it less secure.
The three-tier DB architecture does not allow its clients and database to communicate directly- thus making it comparatively more secure in the long run.