This document discusses database architecture and concepts. It covers the three-level database architecture including the external, conceptual, and internal levels. It describes data independence which provides immunity from changes between the different levels. The document also outlines the functions of a database management system including data processing, transaction support, concurrency control, and more. Different database environments are reviewed such as single-user, multi-user, client-server, and file server configurations.

1. Chapter 2
Database Architecture

2. Today’s Review
Continue 3-Level architecture
Data Independence
Different aspect of DBMS

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

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

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

6. Physical Level
Generally same as Internal
Actual representation of data on the
storage device
In the binary format
OS responsibility

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
BH RH Rana Aslam 120970 5 D001 RH Marya Wasti…
01110011010011100101001010100101010010101…..

12. Data
Independence

13. © Virtual University of Pakistan

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

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

16. Data Independence
Types
• Logical Data Independence
• Physical Data Independence

17. Logical Data
Independence
Changes in conceptual model do not affect the
external views
Immunity of external level from changes at
conceptual level

18. Types of Changes
Adding a new file/index etc.
Adding a new field in a file
Changing type/size
Deleting an attribute

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

20. Changes Examples
Changing file organization
Index implementation, hash, tree etc.
Changing storage medium

21. 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

22. Functions of DBMS
 Data Processing
 A User Accessible Catalog
 Transaction Support
 Concurrency Control Services

23. Functions of DBMS
 Recovery Services
 Authorization Services
 Support for Data Communication
 Integrity Services

24. DBMS Environments
Single User
Multi-user
Teleprocessing
File Servers
Client-Server

25. Teleprocessing
All processing at
a central computer
Dumb Terminals

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

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

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

29. Thanks and