Three-Level Schema Architecture of DBMS
Three-Level Schema Architecture of DBMS
In this tutorial, we will cover the three schema architectures of the respective DBMS (Database Management System), but before that, let discuss the definition of Schema.
What do you understand by the Schema?
Schema is considered the most important concept used in the database management system (DBMS) effectively. Schema can be defined as the overall design of the particular database effectively and efficiently, or it can be defined as the database description.
· Schema can be considered the physical representation of the detailed data that is present in the database management system.
· Schema can be called as the structure for any respective database.
· The respective things that are quite available in the database schema include:
1) Definition related to the database.
2) Particular entities.
3) And the respective components.
· Generally, the database schema usually explains the integrity constraints related to the database, attributes related to the domains, primary key, and foreign key related to all the respective relations.
Three-Schema Architecture in DBMS
In general, the three-level schema architecture related to the effective database management system usually divides the effective database into three levels that, in turn, are used to create a separation between the effective user applications and the physical database. In simple words, it could be defined as the architecture effectively hiding the details of the physical storage from the user.
Moreover, the DBA (Database Administrator) is the person who is quite responsible for making effective changes in the respective database storage without affecting the user’s view.
This architecture usually consists of the three layers of the database management system, which can be included as:
1) External level/ View level
2) Conceptual level
3) Internal level
External level/ View level: External level or the view level can be considered the most important type of the layers in the respective database management system (DBMS). Generally, the external or the view level is defined as the topmost layer in the database management system. It usually provides different views for the same kind of the respective database to the specific user or the group of users effectively. Usually, it provides a flexible security mechanism by hiding the various parts of the respective database from the particular users.
Conceptual or Logical Level: The conceptual or the logic level is usually considered the other most important type of the respective layer in the database management system (DBMS). Generally, the whole database structure could be easily defined by the respective conceptual level. The conceptual or logic level can be considered the middle layer between the physical storage and the user view. The respective things that can be explained by the respective conceptual or the logical level are as follows:
· What kind of data can be stored in the respective database?
· The kind of relationship that must exist among the respective data.
· And what kind of data types is used?
There is only one existence of the conceptual Schema as per the database.
Moreover, at the conceptual or Logical level, the Database administrator and the programmer work effectively. At this level, it mainly concentrates on the effective relational model of the database, and it usually never provides any access as well as the details regarding the storage of the database.
The most important part of the conceptual level is that it is encapsulated with features that usually specify the checks to retain integrity and consistency effectively and efficiently.
Internal level or Physical level: Internal level or the Physical level is usually considered to be another most important type of the Schema or the layer that is efficiently used in the database management system (DBMS). The internal or physical level can be considered the lowest level of the Schema used in database abstraction.
Moreover, the internal or physical level can describe how the data is stored in the effective database. They are also responsible for providing effective and efficient methods to access the data from a particular database.
Some of the advantages of the three-level schema architecture for the database management systems (DBMS) are as follows:
· Data abstraction is quite possible in the three-level schema architecture in a database management system (DBMS).
· It allows every individual to access the same database with different customized views of the respective data.
· And many more etc.