1. Introduction To DBMS

2. Information is data that have been put into a meaningful and useful context and communicated to recipient who uses it to make decisions.
Information helps in eliminating irrelevant and poor data.
More useful and intelligent form.
Integration of information is needed in MIS is done through DBMS

3. Difference between Data and information
Input(Data)
Process
Information (Output)

4. Key attributes of Information
Accuracy- free from mistakes and errors, clear
Timeliness- within given time frame
Relevancy- use of information for particular person

5. Information processing
Information Processing is the acquisition storage, organization, retrieval, display and dissemination of information
People
Goals
Information
Physical Resources

6. Finance
R&D
Production
Production Planning
Marketing
Sales and distribution
production

7. Data – raw facts
Information- refined data
Field – a character or group of characters (alphanumeric or numeric) that has a specific meaning
Record – a set of one or more logically related fields
File – a set of related records

8. Stages of Information System
Stage 0: Manual Information System
Records
Files
Index Cards
Stage 1: Sequential Information Systems
Tapes
slow, non-interactive, redundancy,... .
Stage 2: File Based Information Systems
Disk (direct access)
application program has its own file data dependence
data redundancy
Stage 3: DBMS based Information Systems
Generalized data management software
Transaction processing

9. File Systems
Input
Application
program
Data file
Output

10. File based systems Problems: Data is stored in files
Each file has a specific format
Programs that use these files depend on knowledge about that format
Problems:
No standards
Data duplication
Data dependence
No way to generate ad hoc queries
No provision for security, recovery, concurrency, etc.

11. Disadvantages of File Approach
Data and application dependence
Data isolation
Data redundancy
Redundant storage
Anomalies
Data inconsistency
Violation of data integrity

12. Drawbacks of using file systems
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

13. Drawbacks of using file systems (cont.)
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 accessed 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

14. Collection of interrelated data Set of programs to access the data
DBMS contains information about a particular enterprise
DBMS provides an environment that is both convenient and efficient to use.
Database Applications:
Banking: all transactions
Airlines: reservations, schedules
Universities: registration, grades
Sales: customers, products, purchases
Manufacturing: production, inventory, orders, supply chain
Human resources: employee records, salaries, tax deductions
Databases touch all aspects of our lives

15. Database Definition Database :
is a collection of data, typically describing the activities of one or more related organizations
is a collection of logically related files
a collection of data and information describing items of interest to an organization
A database is a collection of information
DBMS: is a software designed to assist in maintaining and utilizing large collection of data
A database management system (DBMS) is the software than controls that information

16. Purpose of Database Systems
Database management systems were developed to handle the following difficulties of typical file-processing systems supported by conventional operating systems:
Data redundancy and inconsistency
Difficulty in accessing data
Data isolation – multiple files and formats
Integrity problems
Atomicity of updates
Concurrent access by multiple users
Security problems

17. DBMS Functions Data management: Maintaining data independence
storage management
integrity management
manipulation
Maintaining data independence
Security management
Concurrency control
Recovery management
Database communication support
M.G. Erechtchoukova

18. Data Redundancy
Data inconsistency exists when different and conflicting versions of the same data appear in different places.

19. Data Independence External Schema 2 External Schema 3
Logical data
independence
Conceptual
Schema
Physical data
Physical
Schema
independence
Secondary
Storage

20. Data Independence (cont…)
Logical data independence – the immunity of the external schemas to changes in the conceptual schema
Physical data independence – the immunity of the conceptual schema to changes in the physical schema
M.G. Erechtchoukova

21. Data Dictionary Meta-data: Data about users and authorization
Descriptions of data items and relationships among them
Integrity constraints
Data about users and authorization
Used by DBMS to implement data processing
The dictionary or catalog stores information about the database itself
This is data about data or ‘metadata’
Almost every DBMS uses the dictionary

22. Data Integrity Correctness and accuracy of the data
E.g.Primary key constraint

23. Schema Schema – the logical structure of the database
e.g., the database consists of information about a set of customers and accounts and the relationship between them)
Analogous to type information of a variable in a program
Physical schema: database design at the physical level
Logical schema: database design at the logical level

24. Instances
Instance – the actual content of the database at a particular point in time
Analogous to the value of a variable
Physical Data Independence – the ability to modify the physical schema
without changing the logical schema
Applications depend on the logical schema
In general, the interfaces between the various levels and components should
be well defined so that changes in some parts do not seriously influence others.