What is the architecture of a DBMS?

DBMS Architecture

• The DBMS design depends upon its architecture. The basic client/server architecture is used to deal with a large number of PCs, web servers, database servers and other components that are connected with networks.
• The client/server architecture consists of many and a workstation which are connected via the network.
• DBMS depends upon how users are connected to the database to get their request done.

Types of DBMS Architecture

Database architecture can be seen as a single tier or multi-tier. But logically, database architecture is of two types like: 2-tier architecture and 3-tier architecture.

1-Tier Architecture

• In this architecture, the database is directly available to the user. It means the user can directly sit on the DBMS and uses it.
• Any changes done here will directly be done on the database itself. It doesn't provide a handy tool for end users.
• The 1-Tier architecture is used for development of the local application, where programmers can directly communicate with the database for the quick response.

2-Tier Architecture

• The 2-Tier architecture is same as basic client-server. In the two-tier architecture, applications on the client end can directly communicate with the database at the server side. For this interaction, API's like: ODBC, JDBC are used.
• The user interfaces and application programs are run on the client-side.
• The server side is responsible to provide the functionalities like: query processing and transaction management.
• To communicate with the DBMS, client-side application establishes a connection with the server side.

3-Tier Architecture

• The 3-Tier architecture contains another layer between the client and server. In this architecture, client can't directly communicate with the server.
• The application on the client-end interacts with an application server which further communicates with the database system.
• End user has no idea about the existence of the database beyond the application server. The database also has no idea about any other user beyond the application.
• The 3-Tier architecture is used in case of large web application.

Three schema Architecture

• The three schema architecture is also called ANSI/SPARC architecture or three-level architecture.
• This framework is used to describe the structure of a specific database system.
• The three schema architecture is also used to separate the user applications and physical database.
• The three schema architecture contains three-levels. It breaks the database down into three different categories.

The three-schema architecture is as follows:

In the above diagram:

• It shows the DBMS architecture.
• Mapping is used to transform the request and response between various database levels of architecture.
• is not good for small DBMS because it takes more time.
• In External / Conceptual mapping, it is necessary to transform the request from external level to conceptual schema.
• In Conceptual / Internal mapping, DBMS transform the request from the conceptual to internal level.

1. Internal Level

• The internal level has an internal schema which describes the physical storage structure of the database.
• The internal schema is also known as a physical schema.
• It uses the physical data model. It is used to define that how the data will be stored in a block.
• The physical level is used to describe complex low-level data structures in detail.

2. Conceptual Level

• The conceptual schema describes the design of a database at the conceptual level. Conceptual level is also known as logical level.
• The conceptual schema describes the structure of the whole database.
• The conceptual level describes what data are to be stored in the database and also describes what relationship exists among those data.
• In the conceptual level, internal details such as an implementation of the data structure are hidden.
• Programmers and database administrators work at this level.

3. External Level

• At the external level, a database contains several schemas that sometimes called as subschema. The subschema is used to describe the different view of the database.
• An external schema is also known as view schema.
• Each view schema describes the database part that a particular user group is interested and hides the remaining database from that user group.
• The view schema describes the end user interaction with database systems.