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Distributed Database Management System.pptx
- 2. Outlines • Distributed Databases • Distributed Database Management System • Distributed Database Features • Distributed Database Types • Distributed Database Storage • Distributed Database Advantages • Distributed Database Disadvantages
- 4. Distributed Databases • A distributed database is a collection of multiple interconnected databases, which are spread physically across various locations that communicate via a computer network. • Since the databases are all connected, they appear as a single database to the users. • Data is physically stored across multiple sites. • Data in each site can be managed by a DBMS independent of the other sites
- 5. Distributed Database Management System • A distributed database management system (DDBMS) is a centralized software system that manages a distributed database in a manner as if it were all stored in a single location. • It is used to create, retrieve, update and delete distributed databases. • It synchronizes the database periodically and provides access mechanisms by the virtue of which the distribution becomes transparent to the users.
- 6. Distributed Database Management System • It ensures that the data modified at any site is universally updated. • It is used in application areas where large volumes of data are processed and accessed by numerous users simultaneously. • It is designed for heterogeneous database platforms. • It maintains confidentiality and data integrity of the databases.
- 7. Distributed Database Features • Some general features of distributed databases are: • Location independency - Data is physically stored at multiple sites and managed by an independent DDBMS. • Distributed transaction management - Provides a consistent distributed database through commit protocols, distributed concurrency control techniques, and distributed recovery methods in case of many transactions and failures.
- 8. Distributed Database Features • Seamless integration - Databases in a collection usually represent a single logical database, and they are interconnected. • Network linking - All databases in a collection are linked by a network and communicate with each other. • Distributed query processing - Distributed databases answer queries in a distributed environment that manages data at multiple sites.
- 9. Distributed Database Types • There are two types of distributed databases: 1. Homogenous 2. Heterogeneous
- 10. Homogeneous DDBMS • A homogenous distributed database is a network of identical databases stored on multiple sites. • The sites have the same operating system, DDBMS, and data structure, making them easily manageable. • Homogenous databases allow users to access data from each of the databases seamlessly.
- 11. Heterogeneous DDBMS • A heterogeneous distributed database uses different schemas, operating systems, DDBMS, and different data models. • In the case of a heterogeneous distributed database, a particular site can be completely unaware of other sites causing limited cooperation in processing user requests. • The limitation is why translations are required to establish communication between sites.
- 12. Distributed Database Storage • Distributed database storage is managed in two ways: • Replication • Fragmentation
- 13. Replication • In database replication, the systems store copies of data on different sites. • If an entire database is available on multiple sites, it is a fully redundant database. • The advantage of database replication is that it increases data availability on different sites and allows for parallel query requests to be processed.
- 14. Replication • However, database replication means that data requires constant updates and synchronization with other sites to maintain an exact database copy. • Any changes made on one site must be recorded on other sites, or else inconsistencies occur. • Constant updates cause a lot of server overhead and complicate concurrency control, as a lot of concurrent queries must be checked in all available sites.
- 15. Replication
- 16. Fragmentation • When it comes to fragmentation of distributed database storage, the relations are fragmented, which means they are split into smaller parts. • Each of the fragments is stored on a different site, where it is required. • The prerequisite for fragmentation is to make sure that the fragments can later be reconstructed into the original relation without losing data. • The advantage of fragmentation is that there are no data copies, which prevents data inconsistency.
- 19. Distributed Database Advantages • Modular Development - System can be expanded to new locations or units by adding new servers and data to the existing setup and connecting them to the distributed system without interruption. • Reliability • Lower Communication Cost. • Better Response.
- 20. Distributed Database Disadvantages • Costly Software • Large Overhead. Many operations on multiple sites requires numerous calculations and constant synchronization when database replication is used, causing a lot of processing overhead. • Data Integrity • Improper Data Distribution.