Learn DBMS-Purpose of Database System

What is usefulness of the DBMS?

- In the early days, database applications were built on top of file systems

- Drawbacks of using file systems to store data:

Data redundancy and inconsistency
• Multiple file formats, duplication of information in different files

Difficulty in accessing data
• Need to write a new program to carry out each new task
Data isolation — multiple files and formats
Integrity problems
• Integrity constraints (e.g. account balance > 0) become part of program code
• Hard to add new constraints or change existing ones

Atomicity of updates
• Failures may leave database in an inconsistent state with partial updates carried out
- E.g. transfer of funds from one account to another should either complete or not happen at all

Concurrent access by multiple users
• Concurrent access needed for performance
• Uncontrolled concurrent accesses can lead to inconsistencies
- E.g. two people reading a balance and updating it at the same time

Security problems
- Database systems offer solutions to all the above problems