Architecture of DBMS

Architecture of DBMS

• DBMS architectures can vary based on the specific implementation, with some systems incorporating additional components or different arrangements based on their design and intended use cases. However, these core components generally form the foundation of most DBMS architectures.
• The architecture of a Database Management System (DBMS) refers to its overall structure and organization, encompassing various components that work together to manage overall operations regarding data.
• The key components of a typical DBMS architecture are:-

1. 1. Users:
      • These are different individuals or applications interacting with the DBMS.
      • Users can be categorized into different roles like administrators, database designers, and end-users (who query or modify data).
   2. Database Application:
      • These are software programs or applications that interact with the DBMS to perform operations such as data insertion, querying, updating, and deletion.
      • These applications could be anything from simple web interfaces to complex enterprise software.
   3. DBMS Engine:
      • Also known as the Database Engine or Kernel.
      • This is the core component of the DBMS.
      • It interprets and executes queries, manages data storage, handles user requests, and ensures data integrity and security.
      • It consists of several sub-components:
        1. Query Processor: This sub-component receives and processes SQL or other query languages, optimizing them for efficient execution.
        2. Transaction Manager: This sub-component ensures the ACID properties (Atomicity, Consistency, Isolation, Durability) of database transactions.
        3. Storage Manager: This sub-component manages how data is stored on physical storage devices, handling tasks like data indexing, buffering, and file management.
   4. Database Catalog or Data Dictionary:
      • This component stores metadata or information about the structure of the database, such as the schema, data types, constraints, and relationships.
      • It’s used by the DBMS to interpret and manage the database.
   5. Transaction Management System:
      • This component is responsible for managing concurrent access to the database by multiple users or applications, ensuring that transactions are executed in an isolated and consistent manner.
   6. Data Access Layer:
      • This layer provides an interface between the application programs and the DBMS, allowing applications to access and manipulate the data without needing to know the underlying database structure or storage details.
   7. Storage Subsystem:
      • This component deals with physical data storage on disks or other storage devices.
      • It manages the allocation and retrieval of data blocks and optimizes data access.

Three-Level Architecture of DBMS

• The three-level architecture of DBMS is a foundational concept that facilitates the organization, management, and security of databases.
• The three-level architecture of a Database Management System (DBMS) is a framework designed to separate the user applications and the physical database, ensuring data abstraction and independence.
• This architecture is fundamental to understanding how modern DBMSs are structured and operate.
• By separating the user’s view from the physical storage, this architecture supports data abstraction and independence, making databases more flexible and easier to maintain.
• The three-level architecture of DBMS is for achieving data abstraction, data independence, and efficient database management.
• It provides a clear separation between how users interact with data and how data is physically stored, making it easier to manage complex databases.
• The three levels are:

1. External/User Views Level or Schema

• This is the highest level of abstraction and deals with how individual users view the data.
• It includes multiple user views and interfaces.
• At this level, each user or user group sees a customized view of the database. This view includes only the data of interest to the user and hides the rest of the database.
• External schemas are used to define the user views.
• They ensure that users interact with the database in a manner that is relevant to their specific needs without worrying about how the data is stored.
• This level includes user interfaces such as applications, queries, and reports for user views.

2. Conceptual/Logical Level or Schema

• The conceptual level provides a community user view of the database.
• It describes the logical structure of data stored in the database and the relationships among those data.
• It represents the complete view of the data requirements without any concern about how the data will be physically stored.
• The conceptual level ensures logical data independence, meaning that changes in the physical level do not affect the conceptual level.
• This level of schema defines all the logical structure of the entire database for a community of users.

3. Internal/Physical Level or Schema

• This is the lowest level of abstraction and deals with how the data is physically stored in the database.
• Physical storage structure and access methods
• The internal schema of the internal level defines the physical storage structure of the database.
• It describes how the data is stored in terms of files, indexes, and other physical storage details.
• This level deals with the details of data storage and access paths.
• It ensures efficient data storage and retrieval mechanisms.
• The internal level ensures physical data independence, i.e., changes at the physical level do not affect the conceptual level.
• This level includes Physical storage, Indexing, Data compression, etc.

Benefits of Three-Level Architecture of DBMS

There are the following advantages of the three-level architecture of DBMS –

1. Data Abstraction
   • It separates physical storage details from the database design.
   • It simplifies database management and user interactions.
2. Data Independence
   • Logical Data Independence: It changes to the conceptual schema do not affect external schemas.
   • Physical Data Independence: It changes to the internal schema do not affect the conceptual schema.
3. Security
   • It provides a way to enforce security by restricting user access to only relevant data.
4. Customization
   • It allows different users to have customized views of the same database.