Chapter 1
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File Systems and Databases
Prof. Sin-Min Lee
Dept. of Computer Science
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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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.

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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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.

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?
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
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.
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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File System Critique
 File System Data Management
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
File systems require extensive programming in a
third-generation language (3GL).

As the number of files expands, system
administration becomes difficult.

Making changes in existing file structures is
important and difficult.

Security features to safeguard data are difficult to
program and usually omitted.

Difficulty to pool data creates islands of
information.
File System Critique
 Structural and Data Dependence

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Structural Dependence
A change in any file’s structure requires the
modification of all programs using that file.

Data Dependence
A change in any file’s data characteristics requires
changes in all data access programs.


Significance of data dependence is the difference
between the data logical format and the data
physical format.
Data dependence makes file systems extremely
cumbersome from a programming and data
management point of view.
File System Critique
 Field Definitions and Naming Conventions
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A good (flexible) record definition anticipates
reporting requirements by breaking up fields into
their components.

Example:
– Customer Name  Last Name, First Name, Initial
– Customer Address  Street Address, City, State
FIELD
CONTENTS
CUS_LNAME
Customer last name
CUS_FNAME
Customer first name
CUS_INITIAL
Customer initial
CUS_AREACODE
Customer area code
CUS_PHONE
Customer phone
CUS_ADDRESS
Customer street address or box number
CUS_CITY
Customer city
CUS_STATE
Customer state
File System Critique
 Field Definitions and Naming Conventions
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
Selecting proper field names is very important.

Names must be as descriptive as possible within
restrictions.

Naming must reflect designer’s documentation needs
and user’s reporting and processing requirements.
File System Critique
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 Data Redundancy:
Uncontrolled data redundancy sets the
stage for

Data Inconsistency (lack of data integrity)

Data anomalies

Modification anomalies

Insertion anomalies

Deletion anomalies
Figure 1.6
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The Database System Environment
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Figure 1.7
Figure 1.7
Database Systems
 The Database System Components

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Hardware



Computer
Peripherals
Software



Operating systems software
DBMS software
Applications programs and utilities software
Database Systems
 The Database System Components

People

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




Procedures


Systems administrators
Database administrators (DBAs)
Database designers
Systems analysts and programmers
End users
Instructions and rules that govern the design and use of
the database system
Data

Collection of facts stored in the database
Database Systems
 The Database System Components

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
The complexity of database systems depends on
various organizational factors:

Organization’s size

Organization’s function

Organization’s corporate culture

Organizational activities and environment
Database solutions must be cost effective AND
strategically effective.
Database Systems
 Types of Database Systems

Number of Users

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Single-user
– Desktop database

Multiuser
– Workgroup database
– Enterprise database

Scope



Desktop
Workgroup
Enterprise
Database Systems
 Types of Database Systems
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Location



Centralized
Distributed
Use



Transactional (Production)
Decision support
Data warehouse
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