Database management system

1. Introduction to
Database Systems
Lecture: 04

2. An overview of lecture - 3
• Database Architecture
• Data Independence

3. Sequence [Todays Agenda]
Content of Lecture
•Continue 3-L architecture
•Data Independence
•Different Environments of DBMS

4. Level 3
Internal or Physical View
• Concerns about the physical implementation of
the database

5. Internal View
• DBMS chooses type of data structures
• lays out data on storage devices with operating
system access methods

6. Internal View
• Internal record: a single stored record
• Does not just contain what we see at the
conceptual level
• DBMS adds other data

7. Inter-Schema Mappings
• Also a part of 3-level architecture
• External/conceptual mapping
• Conceptual/Internal

8. Ext/Con Mapping
• Specifies mapping between objects in the
external view to those in the logical model

9. Con/Int Mapping
• Specifies mapping between objects in the logical
model to those in the physical model-data
independence

10. 3-Level Architecture
External Level
Conceptual Level
Internal Level
Physical Data
Organization
Ext/Con Mapping
View 1 View 2 View n
Conceptual
Schema
Internal
Schema
Database
User 1 User 2 User n
Con/Int Mapping

11. Name DoB Deps DepId
Rana Aslam 12/09/70 5 D001
Marya Wasti 29/02/80 0 D005
First Name: Rana
Last Name: Aslam
Date of Birth:
12 Sep, 1970
Name: R. Aslam
Age: 24y,10d
Dept: Sales
Saleem
Saleema
01110011010011100101001010100101010010101…..
BH RH Rana Aslam 120970 5 D001 RH Marya Wasti…

12. Data Independence
• A major outcome of 3-L Arch
• The immunity of applications to change in storage structure
and access strategy
12

13. Data Independence
• Changes in the lower levels do not affect the upper levels
• Don’t take it word to word
• Mind the direction please
13

14. Data Independence Types
• Logical Data Independence
• Physical Data Independence
14

15. Logical Data Independence
• Changes in the conceptual model do not affect the external
model
• Immunity of external level from changes at conceptual level
15

16. Type of Changes
• Adding a new file
• Adding a new field in a file
• Changing type/ size
• Deleting an attribute
16

17. Physical Data Independence
• Changes in the internal model do not affect the conceptual
model
• Immunity of Conceptual level from changes at Internal level
17

18. Changes Examples
• Changing file organization
• Index implementation, hash, tree etc.
• Changing storage medium
18

19. 3-Level Architecture
External Level
Conceptual Level
Internal Level
Physical Data
Organization
Ext/Con Mapping
View 1 View n
Conceptual
Schema
Internal
Schema
Database
User 1 User n
Con/Int Mapping
Conceptual Data Ind
Physical
Data Ind

20. DBMS Environments
• Single User
• Multi-user
• Teleprocessing
• File Servers
• Client-Server
20

21. Teleprocessing
All processing at
a central computer
Dumb Terminals

22. File Servers
LAN
File returned Data request
Database
Workstation Workstation
File Server

23. Client-Server
LAN
Selected data returned Data request
Database
Client Client
Server
(with DBMS)

24. Today’s Summary
• Completed 3-L architecture
• Discussed data independence
• Discussion on DBMS
24

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