Updating replicated data in distributed database

For example, in a banking system, an account can be associated the site in which the account has been opened.Similarly, in an airline-reservation system, a flight can be associated with the site at which the flight originates. SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A , SCJP certifications.There can also be partial replication, in which case, some fragment (important frequently· used fragments) of the database are replicated and others are not replicated.There are a number of advantages and disadvantages to replication.

On the other hand, in centralized systems, all queries have to pass through the central computer for processing, which increases the response time.If at any time one master replica is designated to process all the requests, then we are talking about the primary-backup scheme (master-slave scheme) predominant in high-availability clusters.On the other side, if any replica processes a request and then distributes a new state, then this is a multi-primary scheme (called multi-master in the database field).This is necessary for improving the availability of data.There can be full replication, in which a copy of the whole database is stored at every site.Also, in a failure scenario, a failover of replicas is hidden as much as possible.The latter refers to data replication with respect to Quality of Service (Qo S) aspects.Following are the advantages of distributed databases over centralized databases.Modular Development − If the system needs to be expanded to new locations or new units, in centralized database systems, the action requires substantial efforts and disruption in the existing functioning.However, in distributed databases, the work simply requires adding new computers and local data to the new site and finally connecting them to the distributed system, with no interruption in current functions.More Reliable − In case of database failures, the total system of centralized databases comes to a halt.

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