Three Level Architecture of DBMS or Logical DBMS Architecture
The logical architecture defines how data in the database is perceived by users. It is not deals with how the data is handled and processed by the DBMS, but only with how it looks. The process of data storage on the underlying file system is not revealed, and the users can influence the data without worrying about where it is located or how it is really stored. This results in the database having dissimilar levels of abstraction.
The majority of commercial Database Management Systems available today are based on the SPARC / ANSI generalised DBMS architecture, as proposed by the SPARC / ANSI Study Group on Data Base Management Systems. Therefore, this is also called as the SPARC / ANSI model. It separates the system into three levels of abstraction: the physical or internal level, the conceptual level, and the view or external level.