What is the purpose of database management system?

Traditionally, file processing system was used to manage information. It stores data in
various files of different application programs to extract or insert data to appropriate file. File
processing system has several drawbacks due to which database management system is required.
Database management system removes problems found in file processing system. Some of the
major problems of file processing systems are:
1. Data redundancy and inconsistency:
In file processing system, different programmer creates files and writes
application programs to access it. After a long period of time files may exist with
different formats and application programs may be written in many different
programming languages. Moreover, same information may be duplicated in several files.
We have to pay for higher storage and access cost for such redundancy. It may leads
database in inconsistent state because update made may be reflected in one file but it may
not be reflected in another files where same information exist in another files.
2. Difficulty in accessing data:
In file processing system, we can not easily access required data stored in
particular file.
For each new task we have to write a new application program. File processing
system can not allow data to be retrieve in convenient and efficient manner.
3. Integrity problem:
In database, we required to enforce certain type consistency constraints to ensure
the database correctness or to enforce certain business rules. It is in fact called integrity
constraints (e.g. account balance > 0), integrity of database need not to be violated. In file
processing system, integrity constraint becomes the part of application program.
Programmer need to write appropriate code to enforce it. When new constraints are
required to add or change existing one, it is difficult to change program to enforce it.
4. Atomicity problem:
Failures may lead database in an inconsistent state with partial updates. For
example, failure occurs while transferring fund from account A to B. There would be the
case that certain amount from account A is retrieved and it is updated but failure occurs
just before it is deposited to account B, such case may lead database in inconsistent state.
5. Concurrent access problem:
Concurrent accessed increase the overall performance of system providing fast
response time but uncontrolled concurrent accesses can lead inconsistencies in system.
File processing system allow concurrent access but it is unable to coordinate different
application programs so database may lead in inconsistent state. E.g. two people reading
a balance and updating it at the same time.
6. Security problem:
Since file processing system consist large no. of application programs and it is
added in ad hoc manner. So it is difficult to enforce security to each application to allow
accessing only part of data/database for individual database users.