The purpose of DBMS ,

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.

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.

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.

These problems and others led to the development of database management systems.

Leave a Reply

Share This

Sharing is Caring

Share this post with your friends!