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Increased overheads on update: On the drawbacks side, it will need the system to ensure that all replicas of a relation are consistent. This shows that all the replicas of the relation require to be updated at the similar time, resulting in increased overheads. For instance, in a banking system, if account information is replicated at several sites, it is essential that the balance in a particular account should be the similar at all sites.
The problem of controlling concurrent updates by various transactions to replicated data is more difficult than the centralised approach of concurrency control. The management of replicas of relation can be simplified by deciding one of the replicas as the primary copy. For instance, in a banking system, the primary copy of an account may be the site at which the account has been opened. Likewise, in an airline reservation system, the primary copy of the flight may be related with the site at which the flight originates.
Types of Locks There are two necessary types of locks: Binary lock : This locking mechanism has two states for to a data item: locked or unlocked Multiple-mode loc
what is lossless & dependency preserving decomposition ?
1 NF Normal Form The domain of attribute must add only atomic (simple, indivisible) values First normal form (Minimal Form or 1NF) is a normal form need in database normalizat
Define the Boyce-Codd Normal Form with instance and also Compare BCNF and 3NF. Ans: BCNF: For each functional dependency X->Y in a set F of functional dependencies over relati
prototype of a distributed information system for a national car part retail outlet chain.
For every multivalued attribute 'A', we make a new relation R that contains an attribute corresponding to plus the primary key attribute k of the relation that shows the entity typ
Relations create the database. They must satisfy various properties, like no duplicate tuples, no ordering of tuples, and atomic attributes, etc. Relations that satisfy these basic
The basic merits of decomposition. The Advantages of Decomposition 1. Separate person can work on each subsystem. 2. A particular software engineer can specialize in a
Q. Why would you choose a database system instead of simply storing data in operating system file? Define at a base concept in details. Sol. Advantages of Database over Fil
What are the different integrity constraints in RDBMS? The various integrity constraints in RDBMS are as: Primary Key: primary key is a grouping of one or more attributes
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