Database management systems can be classified based on several different criteria. These criteria are given below:
1.      Based on data models (Data models):

Underlying Data Model
Relational (RDBMS)
Relational model
Object-oriented (OODBMS)
Object-oriented data model
Network model
Hierarchical model
Object-Relational (ORDBMS)
Combined features of Object-based & Relational model

2.      Based on number of users:        
Single-user systems:
                Such types of systems support only one user at a time.
Multi-user systems:
                Such types of systems support multiple users concurrently.

Types of database management system and introduction to dbms

3.      Based on purposes or use:
Transactional DBMS:
Decision Support DBMS:
Data warehouse:

4.      Based on site locations:
Centralized DBMS (CDBMS):
Parallel DBMS:
Distribute DBMS:
Client/Server DBMS:

1.    Centralized database system (Centralized dbms architecture)
The following figure illustrates the centralized database system.
Types of database management system (Types of dbms)
Centralized database system

      In a centralized database system, a database is kept at single physical location.
      Also, a single processor is used to provede central control.
      Different users can access this database from local machines or from remote machines.

      Operations such as insert, update, delete, backup, query, recovery are easier to accomplish.

      Problems such as system crash in central computer results in system failure, as no any user can access the database.
      All terminals must have connection with the central computer, and this incurs cost in networking.

2.    Parallel database system (Parallel architecture)
      In a parallel database system, a database is kept in multiple disks.
      Also, multiple processors are used.
      For parallel systems, different architectures can be used, such as –
      Shared memory
      Shared  data storage disk
      Hierarchical, and
      Independent resources.

      Can be used to query extremely large database.
      Can be used to process large number of transactions simultaneously.
      Provides high throughput and better response time.

What is dbms? (What database management system)

      Networking costs are very high for such kind of systems.
      Management of shared resources becomes very complex.

3.    Distribute database system (Distribute architecture)
      In distributed database systems, data is spread across a variety of different databases. In other words, database is distributed over different computers.
      These computers are connected by a communication network.
      Here, an application can operate on data which is spread across multiple databases in different computers.
      Also, each machine can have data and applications of its own.
      So, each machine can act as a server as well as client.
      The following figure illustrates such type of system.
Types of database management system (Types of dbms)
Distributed database system
      Provides greater efficiency and better performance.
      Provides high throughput and better response time.
      Single database can be shared across several distinct client machines.
      Provides local autonomy.

      As database is distributed, recovery from failure is more complex compared to other systems.

4.    Client/Server database system (Client/Server dbms architecture)
      Client/Server database systems contain two components – Clients & Server.
      Application programs are kept at client side, while, database and DBMS software are kept at server side.
      The client computers are called front-end, while, the server computer is called back-end.
The server and client computers are connected to a network. Clients send request to server to access data in a database, and server returns the result according to the request.

Types of database management system (Types of dbms)
Client/Server database system
      More flexible compared to centralized database system.
Provides high throughput and better response time.
Database can be shared in efficient manner.
Server contains all the business logic, while application-client works only as a front end. So, business logic does not need to be distributed across multiple clients.

                        Client/server programming cost in high.
                        Security needs to be implemented in a better way.

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