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Security: Data not needed by local applications is not stored at the site, therefore no unnecessary security violations may exist.
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?
A field-groups statement or an insert statement reverses storage space and transfers values. False.
If the deletion violates referential integrity constraint, then three alternatives are available: Default option: - refuse the deletion. It is the job of the DBMS to describ
What are the ways in which the variable-length records arise in database systems? Storage of many record types in a file. Record types that permit variable lengths for one o
What is the main advantage of the object model? What are its different components? The object model focuses on the logical data structures. Each object model comprises of many
give me a diagram about physical or internal level
What is a recovery scheme? An integral part of a database system is a recovery scheme that can restore the database to the reliable state that existed before the failure.
What is System R? What are its two major subsystems? System R was intended and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its pur
Forward Recovery (Redo): In this system the committed changes made by a transaction are reapplied to a previous copy of the database. In simpler
Which two files are used during operation of the DBMS? Data dictionary and transaction log are two files used during operation of the DBMS.
What is the need of a log in a DBMS? Briefly describe the various types of records that are normally present in a log. Ans: The system log, which is generally writt
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