Lect-1 database management system 1 class

Database management system

1. Introduction to D istributed D atabase system Lecture-01

2. Centralized database Definition: Centralized database management system is the system in which all the data is stored and managed in a single unit. This is also known as central computer database system. 

3. Usage of centralized DBMS Organization Business Company or in institution  Data can be accessed through a network Local Area Network (LAN) or Wide Area Network (WAN).

4. advantage 1-Data integrity Data is more unified as it stored in single computer system and managed. It is easier to communicate and coordinate to get more reliable and meaningful data. 2-Data redundancy Data is centralized and stored in one location only. There is no duplication of data and irrelevancy in data. 3-Data security Due to storage of data in centralized computer system, the security of data needs to be stronger. Centralized database management system is more secure and more efficient. 

5. Disadvantage Slow processing In centralized database management system, data is stored in one location and it access and processing speed is lesser than other management system. It requires more time to access the data from one location . Loss of data In centralized database management system, if any system failure occurs or any data is lost, then it is not recovered.  

6. Distributed database A  distributed database  is a collection of multiple interconnected databases, which are spread physically across various locations that communicate via a computer network . there are a number of databases that may be geographically distributed all over the world. A distributed DBMS manages the distributed database in a manner so that it appears as one single database to users.

7. Distributed databases

8. Features Databases in the collection are logically interrelated with each other. Often they represent a single logical database . Data is physically stored across multiple sites. Data in each site can be managed by a DBMS independent of the other sites.

9. Type of distributed database There are two types of distributed database system with respect to data and its storage. Homogeneous Heterogeneous Homogeneous The homogeneous database system is the network in which all site/systems are homogeneous. The operating system, database management system and data structure used in all these sites are installed in the same vendor. All the data and information is accessed and modified simultaneously. Homogeneous database system is very easy to access and handle. 

10. Homogeneous

11. Heterogeneous Heterogeneous The heterogeneous distributed database management system is the network of two or more databases which has different type of database management systems. These systems can store data in different storage machines. These systems can use different O perating systems D ifferent database management systems like relational, network or hierarchical. Query processing is more complex.

12. Heterogeneous

13. Advantages of Distributed database system Reliable In distributed database management system, if any connected system fails to do work then there is no effect on the performance of the system. It continues functioning and it is more reliable than other simple database management system. Low communication cost Data and information is stored locally in distributed database management system. Its communication cost and data manipulation become easy and less costly.

14. Advantages of Distributed database system Modular development Modulation in distributed database management system is so easy. More systems can be manipulated and installed by just installing and connecting with the distributed database system with no interruption and failure. Better response All the computer system are installed centrally and can process any query with in shortest possible time. It provides faster response due to centralized processing of database management systems. Data recovery Data can be easily recovered in distributed database management systems.

15. Disadvantages of Distributed database system Data integrity Data is updated on multiple sites can cause problems. Data integrity is more complex and very hard to handle. Duplication of data Same type of data is stored in different systems make duplication of data. It takes much space to store the same data in different computer systems in distributed database management systems.

16. Disadvantages of Distributed database system Improper data distribution Improper data distribution can lead to slow response in processing of query. Same data is stored in different computers can create more problems in distributed database management systems. Less processing speed Much communication is needed to a simple query to perform. In this reason ample time period is required to solve a specific problem.