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Wednesday, 5 July 2017
Various disadvantages of file processing system over DBMS
a) Data redundancy and inconsistency
File processing system leads to the usage of many copies of same data. This is data redundancy. If we need to change any of the data, then we need to change the data at all copies. If not, this will lead to inconsistency.
For example, let us assume a file for storing addresses of students. If we make three copies of the address file and store them in three different computers, we say that the data is redundant. If suppose one want to change the address of any students, then the change should be made at all the three computers failing which leads to inconsistent data.
b) Difficulty in accessing data
In a file processing system, to access data differently we need to have different programs.
For example, if you want to access student names from a file, we need a program that does the job. If you want to view only address of all students from a specific city, then we need different program that does the required job. This list goes endless. Hence, it is difficult to access data.
c) Data isolation
Files are stored in different locations, different formats. Thus they are isolated.
For example, one location the student data may be stored in .txt format. In other location, the same file may be stored in .doc format.
d) Integrity problems
Integrity problem arises when the database fails to satisfy certain integrity conditions.
For example, the phone number cannot be longer than 10 digits, bank balance should not go below 1000 etc. The actual problem arises when we would like to include new such conditions with the existing database. It is hard to make those changes.
e) Atomicity problems
The database must be in a consistent state in spite of failures.
For example, let us suppose that you have a savings account with the balance 5000 and a loan account with an outstanding of 3000. This is the old consistent state. Now you would like to transfer 500 to your loan account. If this transaction is successful, then your savings balance should be 4500 and loan outstanding should be 2500. This is the new consistent state. Suppose a failure occurs during this transaction, the database must be in any one of the 2 consistent states mentioned above.
It is hard to maintain atomicity in file processing system due to data redundancy, data isolation etc.
f) Concurrent access anomalies
Simultaneous access of a data item should be handled carefully.
For example, if only one ticket is there and two customers are trying to book the ticket simultaneously, the ticket should be allotted to any one customer.
It is difficult to handle in file processing system due to the fact of data isolation, redundancy etc.
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