CIM

1. 1 File Systems and Databases
Chapter 1 The Worlds
of Database Systems
Prof. Sin-Min Lee
Dept. of Computer Science

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Text Book
NARAYAN S.
UMANATH &
RICHARD W.
SCAMELL, DATA
MODELING AND
DATABASE
DESIGN, 2007
Thomson

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A. Silberschatz, H.F. Korth, S. Sudarshan: Database System
Concepts, 5th Ed., McGraw-Hill, 2006.
GOOD REFERENCE

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Files and Databases
File: A collection of records or documents dealing
with one organization, person, area or subject
(Rowley)
Manual (paper) files
Computer files
Database: A collection of similar records with
relationships between the records (Rowley)
Bibliographic, statistical, business data, images, etc.

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Introducing the Database
Major Database Concepts
Data and information
Data - Raw facts
Information - Processed data
Data management
Database
Metadata
Database management system (DBMS)

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Figure 1.1
Sales per Employee for Each of ROBCOR’S Two Divisions

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Database Systems
Types of Database Systems
Number of Users
Single-user
– Desktop database
Multiuser
– Workgroup database
– Enterprise database
Scope
Desktop
Workgroup
Enterprise

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Database Systems
Types of Database Systems
Location
Centralized
Distributed
Use
Transactional (Production)
Decision support
Data warehouse

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Database
A Database is a collection of stored operational data
used by the application systems of some particular
enterprise (C.J. Date)
Paper “Databases”
Still contain a large portion of the world’s knowledge
File-Based Data Processing Systems
Early batch processing of (primarily) business data
Database Management Systems (DBMS)

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Why DBMS?
History
50’s and 60’s all applications were custom built for particular
needs
File based
Many similar/duplicative applications dealing with collections
of business data
Early DBMS were extensions of programming languages
1970 - E.F. Codd and the Relational Model
1979 - Ashton-Tate and first Microcomputer DBMS

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File Based Systems
Naughty
Nice
Just what
asked for
Coal
Estimation
Delivery
List
Application File
Toys
Addresses
Toys

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From File Systems to DBMS
Problems with file processing systems
Inconsistent data
Inflexibility
Limited data sharing
Poor enforcement of standards
Excessive program maintenance

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DBMS Benefits
Minimal data redundancy
Consistency of data
Integration of data
Sharing of data
Ease of application development
Uniform security, privacy, and integrity controls
Data accessibility and responsiveness
Data independence
Reduced program maintenance

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Terms and Concepts
Data independence
Physical representation and location of data and the use of
that data are separated
The application doesn’t need to know how or where the
database has stored the data, but just how to ask for it
Moving a database from one DBMS to another should not have
a material effect on application program
Recoding, adding fields, etc. in the database should not affect
applications

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Database Environment
CASE
Tools
DBMS
User
Interface
Application
Programs
Repository Database

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Database Components
DBMS
===============
Design tools
Table Creation
Form Creation
Query Creation
Report Creation
Procedural
language
compiler (4GL)
=============
Run time
Form processor
Query processor
Report Writer
Language Run time
User
Interface
Applications
Application
ProgramsDatabase
Database contains:
User’s Data
Metadata
Indexes
Application Metadata

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Types of Database Systems
PC databases
Centralized database
Client/server databases
Distributed databases
Database models

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PC Databases
E.g.:
Access
FoxPro
Dbase
Etc.

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Centralized Databases
Central
Computer

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Client Server Databases
Network
Client
Client
Client
Database
Server

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Distributed Databases
computer
computer
computer
Location A
Location C
Location B
Homogeneous
Databases

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Distributed Databases
Local Network
Database
Server
Client
Client
Comm
Server
Remote
Comp.
Remote
Comp.
Heterogeneous
Or Federated
Databases

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Introducing the Database
Importance of DBMS
It helps make data management more efficient
and effective.
Its query language allows quick answers to ad
hoc queries.
It provides end users better access to more and
better-managed data.
It promotes an integrated view of organization’s
operations -- “big picture.”
It reduces the probability of inconsistent data.

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Figure 1.2
The DBMS Manages the Interaction
Between the End User and the Database

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Introducing the Database
Why Database Design Is Important?
A well-designed database facilitates data
management and becomes a valuable information
generator.
A poorly designed database is a breeding ground
for uncontrolled data redundancies.
A poorly designed database generates errors that
lead to bad decisions.

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Historical Roots
Why Study File Systems?
It provides historical perspective.
It teaches lessons to avoid pitfalls of data
management.
Its simple characteristics facilitate understanding
of the design complexity of a database.
It provides useful knowledge for converting a file
system to a database system.

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Figure 1.3
Contents of the CUSTOMER File

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Table 1.1 Basic File Terminology
Data “Raw” facts that have little meaning unless they have been
organized in some logical manner. The smallest piece of data
that can be “recognized” by the computer is a single
character, such as the letter A, the number 5, or some
symbol such as; ‘ ? > * +. A single character requires one
byte of computer storage.
Field A character or group of characters (alphabetic or numeric)
that has a specific meaning. A field might define a telephone
numbers, a birth date, a customer name, a year-to-date
(YTD) sales value, and so on.
Record A logically connected set of one or more fields that describes
a person, place, or thing. For example, the fields that
comprise a record for a customer named J. D. Rudd might
consist of J. D. Rudd’s name, address, phone number, date
of birth, credit limit, unpaid balance, and so on.
File A collection of related records. For example, a file might
contain data about ROBCOR Company’s vendors; or, a file
might contain the records for the students currently enrolled
at Gigantic University.

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Figure 1.4
Contents of the AGENT File

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A Simple File System
Figure 1.5

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