What is data independence? explain the types of data independence?
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Data independence is the type of data transparency that matters for a centralised DBMS. It refers to the immunity of user applications to changes made in the definition and organization of data.
Physical data independence deals with hiding the details of the storage structure from user applications. The application should not be involved with these issues, since there is no difference in the operation carried out against the data.
The data independence and operation independence together gives the feature of data abstraction. There are two levels of data independence. they are Physical data independence and Logical data independence.
Physical data independence is the ability to modify the physical schema without causing application programs to be rewritten. Modifications at the physical level are occasionally necessary to improve performance. It means we change the physical storage/level without affecting the conceptual or external view of the data. The new changes are absorbed by mapping techniques.Logical data independence is the ability to modify the logical schema without causing application program to be rewritten. Modifications at the logical level are necessary whenever the logical structure of the database is altered (for example, when money-market accounts are added to banking system). Logical Data independence means if we add some new columns or remove some columns from table then the user view and programs should not change. For example: consider two users A & B. Both are selecting the fields "EmployeeNumber" and "EmployeeName". If user B adds a new column (e.g. salary) to his table, it will not effect the external view for user A, though the internal schema of the database has been changed for both users A & B.
Logical data independence is more difficult to achieve than physical data independence, since application programs are heavily dependent on the logical structure of the data that they access.
hope this help you
Physical data independence deals with hiding the details of the storage structure from user applications. The application should not be involved with these issues, since there is no difference in the operation carried out against the data.
The data independence and operation independence together gives the feature of data abstraction. There are two levels of data independence. they are Physical data independence and Logical data independence.
Physical data independence is the ability to modify the physical schema without causing application programs to be rewritten. Modifications at the physical level are occasionally necessary to improve performance. It means we change the physical storage/level without affecting the conceptual or external view of the data. The new changes are absorbed by mapping techniques.Logical data independence is the ability to modify the logical schema without causing application program to be rewritten. Modifications at the logical level are necessary whenever the logical structure of the database is altered (for example, when money-market accounts are added to banking system). Logical Data independence means if we add some new columns or remove some columns from table then the user view and programs should not change. For example: consider two users A & B. Both are selecting the fields "EmployeeNumber" and "EmployeeName". If user B adds a new column (e.g. salary) to his table, it will not effect the external view for user A, though the internal schema of the database has been changed for both users A & B.
Logical data independence is more difficult to achieve than physical data independence, since application programs are heavily dependent on the logical structure of the data that they access.
hope this help you
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Hey !
Data independence allows modification of a scheme definition in one level without affecting a scheme definition in the next higher level.
There are two types of data independence:
1. Physical Data Independence:
Physical Data Independence modifies the scheme followed at the physical level without affecting the scheme followed at the conceptual level.
2. Logical Data Independence:
Whereas Logical Data Independence modifies the conceptual scheme without causing any changes in the schemes followed at view levels.
Data independence allows modification of a scheme definition in one level without affecting a scheme definition in the next higher level.
There are two types of data independence:
1. Physical Data Independence:
Physical Data Independence modifies the scheme followed at the physical level without affecting the scheme followed at the conceptual level.
2. Logical Data Independence:
Whereas Logical Data Independence modifies the conceptual scheme without causing any changes in the schemes followed at view levels.
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