Purpose and functions of Database Management Systems

1.       State the Purpose and functions of Database Management Systems

·         Data redundancy is found- the presence of duplicate data in multiple data files

e.g. Customer Name, NI number, Address is present in several different files on several different systems. Errors are generated, time entering data is wasted.

·         Data inconsistency will become a problem

 e.g. information is duplicated in each system and may be updated in most systems but not necessarily in all – the savings account and loan account may have different addresses for a particular customer.

·         Lack of data independence.

In the bank imagine cases where any change in data format or structure requires a change in all the programs that access the data.

e.g. effort required to change from 3-digit STD to 4-digit STD may be very difficult.

·         Data lacks integrity

This is the quality by which information from the system can be trusted.

·         Lack of flexibility

Creating reports

e.g. in this system a summary of account balances in each separate account would require separate reports for each open account or cutting and pasting into a word processor file – not a satisfactory state of affairs.

·          Data not shareable. Similarly if different departments want to access data this would be very awkward.

Functions of a DBMS

DBMS provides the following functions:

·         Concurrency: concurrent access (meaning 'at the same time') to the same database by multiple users

·         Security: security rules to determine access rights of users

·         Backup and recovery: processes to back-up the data regularly and recover data if a problem occurs

·         Integrity: database structure and rules improve the integrity of the data

·         Data descriptions: a data dictionary provides a description of the data

Role of DBA

 DBA is a full time manager responsible for maintaining DBMS and ensuring accuracy

And the integrity of data.

§  What data should go into the database

 • What relationships should exist between different data items

• Who has permission to read the database information (allocate passwords)

• Who has the authority to update the database.

• Be involved in the design of the database and make changes if necessary

• Keep users informed of any changes

• Maintain the data dictionary

• Provide training to users