The three-level ANSI-SPARC (Standardized Architecture for Relational Databases) architecture is a model that defines the components and relationships of a database management system (DBMS). The ANSI-SPARC architecture is a standard model that is used to design and implement relational databases, and it is based on the three-level structure of the data: the external level, the conceptual level, and the internal level.

The following is a brief overview of the three levels of the ANSI-SPARC architecture:

• External level: The external level represents the view of the database from the perspective of the end user. The external level defines the logical view of the data, and it hides the details of the data storage and implementation from the user. The external level consists of a set of schemas, which are logical structures that represent the data to the user.
• Conceptual level: The conceptual level represents the view of the database from the perspective of the database administrator. The conceptual level defines the overall structure and organization of the data, and it hides the details of the physical storage and implementation from the database administrator. The conceptual level consists of a single schema, which is the logical model of the data that is shared by all users.
• Internal level: The internal level represents the physical view of the database, and it defines the details of how the data is stored and accessed on the computer. The internal level consists of a set of physical structures, such as data files, indexes, and buffers, which are used to store and access the data.

The three levels of the ANSI-SPARC architecture are designed to provide a separation of concerns between the end user, the database administrator, and the physical storage of the data. The external and conceptual levels provide a logical view of the data that is independent of the physical implementation, which allows the DBMS to support multiple views of the data and to hide the details of the physical storage from the user. The internal level provides the physical implementation of the data, and it is responsible for storing and accessing the data on the computer.

Overall, the ANSI-SPARC architecture is a standard model for designing and implementing relational databases, and it provides a logical and physical separation of concerns that allows the DBMS to support multiple views of the data and to hide the details of the physical storage from the user.