1 1 file systems and databases chapter 1 prof. sin-min lee dept. of computer science
TRANSCRIPT
11 File Systems and DatabasesChapter 1
Prof. Sin-Min Lee
Dept. of Computer Science
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Introducing the DatabaseIntroducing 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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Introducing the DatabaseIntroducing 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 DatabaseIntroducing 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 RootsHistorical 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 TerminologyData “Raw” facts that have little meaning unless they have been
organized in some logical manner. The smallest piece of datathat can be “recognized” by the computer is a singlecharacter, such as the letter A, the number 5, or somesymbol such as; ‘ ? > * +. A single character requires onebyte of computer storage.
Field A character or group of characters (alphabetic or numeric)that has a specific meaning. A field might define a telephonenumbers, 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 describesa person, place, or thing. For example, the fields thatcomprise a record for a customer named J. D. Rudd mightconsist of J. D. Rudd’s name, address, phone number, dateof birth, credit limit, unpaid balance, and so on.
File A collection of related records. For example, a file mightcontain data about ROBCOR Company’s vendors; or, a filemight contain the records for the students currently enrolledat 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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File System CritiqueFile System Critique
File System Data Management
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.
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File System CritiqueFile System Critique Structural and Data Dependence
Structural DependenceA change in any file’s structure requires the modification of all programs using that file.
Data DependenceA 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.
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File System CritiqueFile System Critique Field Definitions and Naming Conventions
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
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File System CritiqueFile System Critique
Field Definitions and Naming Conventions
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.
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File System CritiqueFile System Critique Data Redundancy:
Uncontrolled data redundancy sets the stage for
Data Inconsistency (lack of data integrity)
Data anomalies
Modification anomalies
Insertion anomalies
Deletion anomalies
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Figure 1.6
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Figure 1.7
The Database System Environment
Figure 1.7
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Database SystemsDatabase Systems
The Database System Components Hardware
Computer Peripherals
Software Operating systems software DBMS software Applications programs and utilities software
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Database SystemsDatabase Systems The Database System Components
People Systems administrators Database administrators (DBAs) Database designers Systems analysts and programmers End users
Procedures Instructions and rules that govern the design and use of
the database system
Data Collection of facts stored in the database
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Database SystemsDatabase Systems The Database System Components
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.
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Database SystemsDatabase 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 SystemsDatabase Systems
Types of Database Systems Location
Centralized Distributed
Use Transactional (Production) Decision support Data warehouse
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