Data abstraction is divided into several levels, the role of each level is what

Physical layer: The lowest level of abstraction that describes how data is actually stored. The physical layer describes the complex underlying data structures in detail and is what the database vendors that develop the DBMS should study.

Logical layer: An abstraction that is slightly higher than the physical level, describing what data is stored in the database and what relationships exist between the data. Thus the entire database can be described by a few relatively simple structures. Although the implementation of a simple logical layer structure involves a complex physical layer structure, the user of the logical layer does not have to know about this complexity. The logical layer abstraction is used by database administrators and database application developers who must determine what information should be kept in the database.

The view layer: The most hierarchical abstraction, but only one part of the entire database is described. Although the logical layer is a relatively simple structure, but because of the large size of the database, there are still some procedural complexity. The end user of the database system does not need to be concerned with all the information, but only the part of the database. The view abstraction layer is defined precisely to make it easier for users to interact with the system. The system can provide multiple views for the same database, and the view guarantees the security of the data.