Transcript File Systems and Databases - Department of Computer Science

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Chapter 1 The Worlds
of Database Systems
File Systems and Databases
Prof. Sin-Min Lee
Dept. of Computer Science
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Tuesday Thursday
10:15 – 11:30
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Text
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Book
NARAYAN
S.
UMANATH &
RICHARD W.
SCAMELL, DATA
MODELING AND
DATABASE
DESIGN, 2007
Thomson
GOOD
REFERENCE
A. Silberschatz, H.F. Korth, S. Sudarshan: Database System
Concepts, 5th Ed., McGraw-Hill, 2006.
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The
mediocre teacher tells.
The
good teacher explains.
The
superior teacher
demonstrates.
The
great teacher inspires.
Files and Databases
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 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)
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Bibliographic, statistical, business data, images, etc.
Introducing the Database
Major Database Concepts
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 Data
and information

Data - Raw facts

Information - Processed data
 Data
management
 Database
 Metadata
 Database
management system (DBMS)
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Sales per Employee for Each of ROBCOR’S Two Divisions
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Figure 1.1
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Database Systems
 Types of Database Systems

Number of Users
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Single-user
– Desktop database

Multiuser
– Workgroup database
– Enterprise database
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Scope



Desktop
Workgroup
Enterprise
Database Systems
 Types of Database Systems
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Location

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Centralized
Distributed
Use
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Transactional (Production)
Decision support
Data warehouse
Database
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 A Database is a collection of stored operational data
used by the application systems of some particular
enterprise (C.J. Date)

Paper “Databases”


File-Based Data Processing Systems


Still contain a large portion of the world’s knowledge
Early batch processing of (primarily) business data
Database Management Systems (DBMS)
Why DBMS?
 History
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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
File Based Systems
Application
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Delivery
List
Coal
Estimation
Just what
asked for
File
Toys
Addresses
Naughty
Nice Toys
From File Systems to DBMS
 Problems with file processing systems
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Inconsistent data
Inflexibility
Limited data sharing
Poor enforcement of standards
Excessive program maintenance
DBMS Benefits
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
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
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
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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
Terms and Concepts
 Data independence
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Physical representation and location of data and the use of
that data are separated
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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
Database Environment
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CASE
Tools
Repository
User
Interface
DBMS
Application
Programs
Database
Database Components
DBMS
===============
Design tools
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Database
Database contains:
User’s Data
Metadata
Indexes
Application Metadata
Table Creation
Form Creation
Query Creation
Report Creation
Procedural
language
compiler (4GL)
=============
Run time
Form processor
Query processor
Report Writer
Language Run time
Application
Programs
User
Interface
Applications
Types of Database Systems
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

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
PC databases
Centralized database
Client/server databases
Distributed databases
Database models
PC Databases
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E.g.:
Access
FoxPro
Dbase
Etc.
Centralized Databases
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Central
Computer
Client Server Databases
Client
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Client
Network
Database
Server
Client
Distributed Databases
Location C
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Location B
computer
computer
computer
Location A
Homogeneous
Databases
Distributed Databases
Client
Heterogeneous
Or Federated
Databases
Database
Server
Remote
Comp.
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Local Network
Comm
Server
Client
Remote
Comp.
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Introducing the Database
 Importance of DBMS
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It helps make data management more efficient
and effective.

Its query language allows quick answers to ad
hoc queries.
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It provides end users better access to more and
better-managed data.

It promotes an integrated view of organization’s
operations -- “big picture.”
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It reduces the probability of inconsistent data.
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The DBMS Manages the Interaction
Between the End User and the Database
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Figure 1.2
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Introducing the Database
 Why Database Design Is Important?
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A well-designed database facilitates data
management and becomes a valuable information
generator.
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A poorly designed database is a breeding ground
for uncontrolled data redundancies.
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A poorly designed database generates errors that
lead to bad decisions.
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Historical Roots
 Why Study File Systems?
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It provides historical perspective.
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It teaches lessons to avoid pitfalls of data
management.
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Its simple characteristics facilitate understanding
of the design complexity of a database.
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It provides useful knowledge for converting a file
system to a database system.
Contents of the CUSTOMER File
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Figure 1.3
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Table 1.1 Basic File Terminology
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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.
Contents of the AGENT File
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Figure 1.4
A Simple File System
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Figure 1.5
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