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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.
A Relation Schema represented by R(A1, A2, ..., An) is made up of the relation name the list of attributes and R Ai that it contains. A relation is described as a set of tuples
The following variant of the primary copy asynchronous-update replication protocol has been proposed for totally replicated systems. (a) A transaction executing at site A updat
Given the following set of functional dependencies {cf?bg, g?d, cdg?f, b?de, d?c} defined on R(b,c,d,e,f,g) a.Find a non-redundant cover. b.Find a canonical cover.
Define tuple variable Tuple variable is a type of variable whose domain is the set of all tuples.
what should be included in this???
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Hi I have got an assignment for making an er diagram for market management software can any budy help me?
What functions does a data dictionary perform? In a (DBMS)data management system, the principal functions performed by the data dictionary are Management of data defini
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