MANAGING DATA RESOURCES

Topics: Database, SQL, Relational model Pages: 37 (1048 words) Published: February 9, 2015
c h a p t e r

7

MANAGING
DATA
RESOURCES
7.1

© 2002 by Prentice Hall

LEARNING OBJECTIVES
• COMPARE TRADITIONAL FILE
ORGANIZATION & MANAGEMENT
TECHNIQUES
• DESCRIBE HOW DATABASE
MANAGEMENT SYSTEM
ORGANIZES
INFORMATION
*

7.2

© 2002 by Prentice Hall

LEARNING OBJECTIVES
• IDENTIFY TYPES OF DATABASE,
PRINCIPLES OF DATABASE DESIGN
• DISCUSS DATABASE TRENDS
*

7.3

© 2002 by Prentice Hall

MANAGEMENT CHALLENGES
• TRADITIONAL DATA FILE
ENVIRONMENT
• DATABASE APPROACH TO DATA
MANAGEMENT
• CREATING DATABASE
ENVIRONMENT
• DATABASE TRENDS
*
7.4

© 2002 by Prentice Hall

MANAGEMENT CHALLENGES
1. ORGANIZATIONAL OBSTACLES:
Challenges existing power structure,
requires organizational restructure
2. COST / BENEFIT CONSIDERATIONS:
Large initial costs, delayed benefits,
tangible, intangible
*
7.5

© 2002 by Prentice Hall

FILE ORGANIZATION
• BIT: Binary Digit (0,1; Y,N; On,Off)
• BYTE: Combination of BITS which
represent a CHARACTER
• FIELD: Collection of BYTES which
represent a DATUM or Fact
• RECORD: Collection of FIELDS which
reflect a TRANSACTION
*
7.6

© 2002 by Prentice Hall

FILE ORGANIZATION
• FILE: A Collection of similar
RECORDS
• DATABASE: An Organization’s
Electronic Library of FILES
organized to serve business
applications
*
7.7

© 2002 by Prentice Hall

FILE ORGANIZATION
• ENTITY: Person, place, thing, event
about which data must be kept
• ATTRIBUTE: Description of a
particular ENTITY
• KEY FIELD: Field used to retrieve,
update, sort RECORD
*
7.8

© 2002 by Prentice Hall

KEY FIELD
Field in Each Record
Uniquely Identifies THIS Record
For RETRIEVAL
UPDATING
SORTING
*
7.9

© 2002 by Prentice Hall

PROBLEMS WITH TRADITIONAL FILE
ENVIRONMENT







7.10

DATA REDUNDANCY
PROGRAM / DATA DEPENDENCY
LACK OF FLEXIBILITY
POOR SECURITY
Flat
File
LACK OF DATA
SHARING &
AVAILABILITY
*
© 2002 by Prentice Hall

SEQUENTIAL VS. DIRECT
FILE ORGANIZATION
• SEQUENTIAL: Tape oriented; one file
follows another; follows physical
sequence
• DIRECT: Disk oriented; can be
accessed without regard to physical
sequence
*
7.11

© 2002 by Prentice Hall

FILING METHODS
• INDEXED SEQUENTIAL ACCESS METHOD (ISAM) :
– EACH RECORD IDENTIFIED BY KEY
– GROUPED IN BLOCKS AND CYLINDERS
– KEYS IN INDEX

• VIRTUAL STORAGE ACCESS METHOD (VSAM) :
– MEMORY DIVIDED INTO AREAS & INTERVALS
– DYNAMIC FILE SPACE

VSAM WIDELY USED FOR RELATIONAL
DATABASES
• DIRECT FILE ACCESS METHOD
*
7.12

© 2002 by Prentice Hall

DIRECT FILE ACCESS METHOD

• EACH RECORD HAS KEY FIELD
• KEY FIELD FED INTO TRANSFORM
ALGORITHM
• ALGORITHM GENERATES PHYSICAL
STORAGE LOCATION OF RECORD
(RECORD ADDRESS)
*

7.13

© 2002 by Prentice Hall

DATABASE MANAGEMENT SYSTEM (DBMS)

SOFTWARE TO CREATE & MAINTAIN
DATA
ENABLES BUSINESS APPLICATIONS
TO EXTRACT DATA
INDEPENDENT OF SPECIFIC
COMPUTER PROGRAMS
*
7.14

DBM

© 2002 by Prentice Hall

COMPONENTS OF DBMS:
• DATA DEFINITION LANGUAGE:
– Defines data elements in database

• DATA MANIPULATION LANGUAGE:
– Manipulates data for applications

• DATA DICTIONARY:
– Formal definitions of all variables in
database, controls variety of database
contents, data elements
7.15

*

DBM

© 2002 by Prentice Hall

STRUCTURED QUERY LANGUAGE (SQL)

EMERGING STANDARD
DATA MANIPULATION LANGUAGE
FOR RELATIONAL DATABASES
*

7.16

DBM

© 2002 by Prentice Hall

ELEMENTS OF SQL
• SELECT: List of columns from tables
desired
• FROM: Identifies tables from which
columns will be selected
• WHERE: Includes conditions for
selecting specific rows, conditions
for joining multiple tables
*
7.17

DBM

© 2002 by Prentice Hall

TWO VIEWS OF DATA
• PHYSICAL VIEW: Where is data physically?
– DRIVE, DISK, SURFACE, TRACK, SECTOR
(BLOCK), RECORD
– TAPE, BLOCK, RECORD NUMBER (KEY)
• LOGICAL VIEW: What data is needed by
application?
–...
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