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3. Lack of Data Sharing: Since each department is dealing with its own copy of data files and the structure of these
files may vary significantly. Across the departments, sharing data becomes a challenge, often an impossible
task.
4. Lack of Design: As each department manages its data, it may not have access to expert advice on how to organise
the data into files in a manner that enables easy processing.
The problems mentioned above are handled smoothly by DBMS, as discussed in the next section.
9.1.3 Advantages and Disadvantages of DBMS
The Data Base Management Systems offer several advantages over conventional file systems as mentioned below:
1. Sharing Data: As the DBMS maintains a single data repository, all users have shared access to the same data.
2. Lack of Data Redundancy: Storing the data centrally in a single repository avoids the problem of data redundancy.
Centralized storage and control of data leads to: reduced redundancy, integrity of data, security, data independence.
3. Data Independence: Changes in the data structure, such as adding a new column in a table, do not affect
existing application programs. Similarly, a change in the data type of an attribute of interest, say, UserID from an
integer to a long integer, does not affect existing application programs because users access data through the DBMS
interface.
Data Independence: Columns may be added or deleted, data types may change, but applications programs do not change.
4. Database Authorization: The DBMS authenticates access to the database based on the user name and password.
Indeed, A DBMS can also enforce authorisation based on data values stored in the database; for example, a user
may be allowed to access the details of employees whose salary does not exceed `75000.
5. Backup and Recovery: A DBMS provides a measure of safety by providing support for backup and recovery of data.
In the case of some user error, hardware failure, or any catastrophic event, the DBMS can recover the database
from the point, it was failed. Further, the DBMS maintains a historical record of all changes made to the database
and can recover the database from any point in time.
6. Integrity: A DBMS ensures the correctness of data stored by introducing various integrity constraints. For example,
each employee must have a unique id. Every employee's date of birth should lie within a reasonable range, and
no employee should be allocated to a department that does not exist in the organisation. DBMS can also enforce
constraints like the date of birth of an employee cannot be left unspecified. These restrictions provide a way to
ensure the integrity of data.
Database Integrity: Consistent and correctness of data.
Having all these advantages, DBMS also have a few disadvantages as follows:
1. Initial Cost: Developing applications based on a DBMS involves hardware and software costs. Further, there may be
a need to train employees.
2. Complexity: As a DBMS offers various functionalities for a wide variety of users (like the sharability and integrity
of data, enforcement of access rights to data, and support for data manipulation), it becomes a large and complex
software.
234 Touchpad Informatics Practices-XI

