Logical Level:

Logical Level: The middle level in the three level architecture are known as logical or conceptual level. It describes the entire structure of the database such as entities, attributes, data types, relationship, constraints on the data and user operations. It hides the details of the physical storage structures that contains further information that may not be important to be shown.

The conceptual level support the external level to represent the data to end user as they need. This level is relatively constant and the DBA designs it after determining the present and the future information needs of the organization. However, to expand the conceptual level, the DBA adds new subject to fulfill the requirements of the organization, without affecting the external level.

The conceptual level is defined by means of the conceptual schema which include the definition of each of the various conceptual record types. The conceptual schema is a complete description of the information of database structure such as every record type with all its fields. It also include security and integrity rules. The conceptual schema is written in DDL, compiled by DBMS and stored in the data dictionary. The DBMS uses the conceptual schema to create the logical record interface, which defines and creates the working environment for the conceptual level to present data to end users. Actually, conceptual level is a collection of logical records of the data file to represent the information.