There are four basic components of Database Management System:
(i) Data: Raw facts which we want to feed in the computer.
(ii) Hardware: On which the data to be processed.
(iii) Software: The interface between the hardware and user, by which the data will change into the information.
(iv) User: There are so many types of users some of them are application programmer, end case users and DBA.
Purpose of Database Systems:
(i) To see why database management systems are necessary, let's look at a typical ``
File-Processing System'' supported by a conventional operating system.
The application is a savings bank:
• Savings account and customer records are kept in permanent system files.
• Application programs are written to manipulate files to perform the following tasks:
Debit or credit an account.
Add a new account.
Find an account balance.
Generate monthly statements.
(ii) Development of the System proceeds as follows:
• New application programs must be written as the need arises.
• New permanent files are created as required.
• But over a long period of time files may be in different formats, and
• Application programs may be in different languages.
(iii) So we can see there are problems with the Straight File-Processing Approach:
• Data Redundancy and Inconsistency:
Same information may be duplicated in several places.
All copies may not be updated properly.
• Difficulty in Accessing Data :
May have to write a new application program to satisfy an unusual request.
E.g. find all customers with the same postal code.
Could generate this data manually, but a long job.
• Data Isolation :
Data in different files.
Data in different formats.
Difficult to write new application programs.
• Multiple Users :
Want concurrency for faster response time.
Need protection for concurrent updates.
E.g. two customers withdrawing funds from the same account at the same time - account has $500 in it, and they withdraw $100 and $50. The result could be $350, $400 or $450 if no protection.
• Security Problems :
Every user of the system should be able to access only the data they are permitted to see.
E.g. payroll people only handle employee records, and cannot see customer accounts; tellers only access account data and cannot see payroll data.
Difficult to enforce this with application programs.
• Integrity Problems :
Data may be required to satisfy constraints.
E.g. no account balance below $25.00.
Again, difficult to enforce or to change constraints with the file-processing approach.
Above all problems lead to the development of Database Management Systems.
• An organized and comprehensiveness of recording the result of the firms activities.
• A receiver of data to be used in meeting the information requirement of the MIS users.
• Reduced data redundancy.
• Reduced updating errors and increased consistency.
• Greater data integrity and independence from applications programs.
• Improved data access to users through use of host and query languages.
• Improved data security.
• Reduced data entry, storage, and retrieval costs.
• Facilitated development of new applications program.
• Standard can be enforced: Standardized stored data format is particularly desirable as an old data to interchange or migration (change) between the system.
• Conflicting requirement can be handled.
• It increases opportunity for person or groups outside the organization to gain access to information about the firms operation.
• It increases opportunity for fully training person within the organization to misuse the data resources intentionally.
• The data approach is a costly due to higher H/W and S/W requirements.
• Database systems are complex (due to data independence), difficult, and time-consuming to design.
• It is not maintain for all organizations .It is only efficient for particularly large organizations.
• Damage to database affects virtually all applications programs.
• Extensive conversion costs in moving form a file-based system to a database system.
• Initial training required for all programmers and users.