According to the three tier architecture of the database, the system is divided into three levels. These levels are related to each other but independent, which means a change in one level will not reflect in the level below.
Three tier Architecture in DBMS
Physical Level – This is the level where the information about the location of the database is kept. Many DBMS users are not aware of where these items are located. In layman’s words, the physical level of a database specifies how the data is kept on discs and tapes and provides information on other storage features.
Conceptual Level – This is the level where data is kept in the form of tables. For example, the Employee table contains the employee id and employee name as attributes. These will be visible to the users but the users will have no idea about the storage of the data.
External Level – A view of the data in terms of conceptual level tables is specified by an external level. A certain user category’s demands are served by each external level view.
For example, the manager of a company wants to see information about the employees and their salaries. Whereas, an employee of the company wants to see information such as active projects, increment periods, etc. So, different views can be generated for different users. One of the uses of the external level is data abstraction.
Data Independence
Data independence means, that the change in one level should not reflect changes in another level. The types of data independence present in this architecture are –
Physical Data Independence – Any change in the physical level which means the storage structure of the database should not lead to a change in the conceptual or external level. This data independence is implemented by most the DBMS.
Conceptual Data Independence – Any change in conceptual schema should not lead to a change in the external schema which means adding or deleting attributes should not lead to a change in the user’s view of the database.
Advantages of database management system
Data Abstraction – Views can be created in a database and the specific type of user will be able to see the information of his need.
Concurrent access to data – Data can be concurrently accessed by different users which were not allowed in the file system
Applying of integrity constraints – Integrity constraints can be applied in a database due to which different tables can be linked and prevented inconsistency.
Distributed Storage – Data can be stored at a remote location and accessed in different parts of the world.
Backup and Recovery – Data can be backed up and if system failure exists then the backed-up data can be loaded.
So, in this article, we learned about the three-tier architecture of a database.
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