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But how can we carry out fragmentation? Fragmentation may be carried out as per the following rules:
a) Completeness: This rule makes sure that there is no loss of data while fragmentation. If a relation is decomposed into fragments, then every data item must appear in at least single fragment.
b) Reconstruction: This rule makes sure preservation of functional dependencies. It should be possible to describe a relational operation that will reconstruct the relation from its fragments.
c) Disjointness: A data item that shows in a fragment should not show in any other fragment. Though, a typical fragmentation known as vertical fragmentation is an exception to this rule. In vertical fragmentation the primary key attributes must be repeated to permit reconstruction of original relation.
This rule makes sure minimization of data redundancy. What are the dissimilar types of fragmentation?
Define rotational latency time. The time spent waiting for the sector to be accessed to appear under the head is known as the rotational latency time.
Which file organization provides very fast access to any arbitrary record of a file? Hashed file organization provides very fast access to any arbitrary record of a file.
What is trigger Triggers are statements that are implemented automatically by the system as the side effect of a change to the database.
Define the notation for classes and atrributes The notation for class, attribute, and operations are shown below: Figure: Class with attributes and operations A
Rules Of Data Normalisation Let us now summarise Normalisation with the help of various clean rules. The following are the necessary rules for the Normalisation process: 1.
What is Foreign Key Foreign Key: Sometimes we may have to work with an attribute that does not have a primary key of its own. To recognize its rows, we have to use the primar
what is the importance of back up files
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Describe log based recovery The most usably structure for recording data base modification is the LOG the log is a sequence of log records recording all the update activities i
Enumerate or state the steps in creating a relevant database of a shop.
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