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Multivalued dependency

In general, a multivalued dependency occurs when a relation R has attributes A, B, and C such thatA determines a set of values for B, A determines a set of values for C, and B and C are independent of Read More …

Partial dependency

A functional dependency that holds in a relation is partial when removing one of the determining attributes gives a functional dependency that holds in the relation.Eg if {A,B} → {C} but also {A} → {C} then {C} is partially functionally Read More …

Full functional dependency

An attribute B is fully functionally dependent on A if the B can be determined by whole of A not by any proper subset of A. A functional dependency X → Y is a full functional dependency if removal of Read More …

Functional Dependency

Normalization is based on the concept of functional dependency. A functional dependency is a type of relationship between attributes.Attribute of set of attributes on the left side are called determinant and on the right are called dependentsLike R (a, b, Read More …

Inference Rules

Rules of Inference for functional dependencies, called inference axioms or Armstrong axioms, after their developer, can be used to find all the FDs logically implied by a set of FDs. These rules are sound , meaningthat they are an immediate Read More …

Normalization

Normalization transforms arbitrary relation schemes into ones without these problems. A relation with one or more of the above mentioned anomalies is split into two or more relations of a higher normal form.Normal Forms Normalization is basically; a process of Read More …

Normalization

Eliminate various anomaliesRepetition anomaly, Update anomaly, Insertion anomaly, Deletion anomaly.The normal forms are based on certain dependency structures. BCNF and lower normal forms are based on functional dependencies (FDs), 4NF is based on multivalued dependencies, and 5NF is based on Read More …

Distributed Concurrency Control:

Concurrency control involves the synchronization of accesses to the distributed database, such that the integrity of the database is maintained.The alternative solutions are pessimistic and optimistic.

Transparent Management of Distributed and Replicated Data

Transparency refers to separation of the higher-level semantics of a system from lower-level implementation issues. In other words, a transparent system “hides” the implementation details from users. The advantage of a fully transparent DBMS is the high level of support Read More …

Distributed DBMS

Distributed DBMS is then defined as the software system that permits the management of the distributed database and makes the distribution transparent to the users.Distributed database are much complex than centralized environment. Data is remotely available at different sites so Read More …

Why do we distribute at all?

Better corresponds to the organizational structure of today’s widely distributed enterprises, and that such a system is more reliable and more responsive.Better able to cope with the large-scale data management problems that we face today, by using a variation of Read More …

What is Distributed Computing System?

A number of autonomous processing elements that are connected through a computer network and that cooperate in performing their assigned tasks.The thing being distributed—Processing logic, Functions, Data, Control, All are relevant and important here