Download File Processing and Data Management Concepts

Chapter File Processing and Data
15
Management Concepts
A field may be a single character or number, or it
may be composed of many characters or
numbers.
 Logical grouping of fields are called records.
 Records are groups of data items that concern
a certain entity such as an employee, a
customer, a vendor, or an invoice.
 A record structure has occurrences, also called
instances.
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Introductory Terminology
In a fixed-length record, both the number of fields
and the length of each field are fixed.
 Most records stored on direct-access storage
devices (DASDs) are fixed length.
 In variable-length records, the width of the field
can be adjusted to each data occurrence.
 A trailer record is an extension of a master record.

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Introductory Terminology
The terms segment, group, and node(simpul)
are shorthand for repeated groups.
 A segment can be written as follows:
 PART (PART_NO, PNAME, TYPE, COST)
 SUPPLIER (PVEND)
 LOCATION (WARHSE, LOC)

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Introductory Terminology

Segments, unlike simple records, have
parents and children.
Part
Supplier
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Location
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Introductory Terminology
A key or record key is a data item or
combination of data items that uniquely
identifies a particular record in a file.
 What is a primary (sort) key?
 It is the first field used to sort the records
in a file.
 What is a secondary (sort) key?

 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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Introductory Terminology
It is a field used to determine relative
position among a set of records when the
primary key has the same value in each
record of the set.
 What is relative random order?
 The term relative random order applies to
a field on which the file is not sorted.

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The Evolution of Database
Technology
Period
Event
Related Database
Technique
1960s
Mainframe
environments
File Systems
Database
management systems
Database
management
On-line information
services
Text management
 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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The Evolution of Database
Technology
Period
Event
Related Database
Technique
1970s
Expert systems
Object-oriented
programming
Inference and
deduction
Inheritance and
abstraction
1980s
Hypertext systems
Association
1990s
Intelligent
database systems
Combination of
techniques
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Database Management Systems
and Their Architecture
Conceptual
Level
Logical
Level
Database contents
Uses of database
Desired reports
Information to be reviewed
Logical data structures:
•Tree (hierarchical)
•Network
•Relational
 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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Database Management Systems
and Their Architecture
Physical
Level

Access methods:
•Sequential
•Indexed-sequential
•Direct
The entity-relationship (E-R) data model
is a conceptual model for depicting the
relationships between segments in a
database.
 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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Conceptual Architecture
The term entity is used instead of segment.
 The term attribute is used to refer to
individual fields or data items.
 The object-oriented modeling technique
(OMT) is a conceptual model for depicting
the relationships between segments in a
database that views the components of the
system being modeled as object classes.

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Logical Data Structures


1
2
3
The relationships that exist between the
segments in the database are determined by
the logical data structure, also called the
schema or database model.
What are the three major models of logical
data structure?
Tree or hierarchical structures
Network structures
Relational models
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Logical Data Structures


In a tree structure each node represents a set of fields
(i.e., a segment), and a node is related to another
node at the next highest level of the tree.
A child node cannot have more than one parent.
A
B
C
F
D
G
H
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E
I
J
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Logical Data Structures


A network structure is one that allows a child
segment to have more than one parent.
A network is a more general data structure than a
tree.
A
B
C
D
E
F
G
H
J
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I
K
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Logical Data Structures
There are various ways to implement tree
and network structures.
 In a list organization each record contains
one or more pointers (fields) indicating the
address of the next logical record with the
same attribute(s).
 A record may be a part of several lists.

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Logical Data Structures
A ring structure differs from a list structure
in that the last record in the ring list points
back to the first record.
 What is a multiple-ring structure?
 In this type of structure several ring
organizations pass through individual
records.

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Logical Data Structures
List Structure
Location of
first record
Index
2
1
Records
1
Attribute
Pointer field to
next record
Red
Blue
2
4
3
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End-of-list
indicator
4
5
5
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Logical Data Structures
Ring Structure
Location of
first record
Index
2
3
Records
1
Attribute
Pointer field to
next record
Va
Ky
2
4
3
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Pointer field to
first record
4
5
5
2
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Logical Data Structures
What is the relational model?
 This model is a logical data structure that
views the database as a collection of twodimensional tables.
 Information is extracted from tables using
relational algebra.
 Certain rules called normal forms govern
the creation of tables.

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Logical Data Structures
What are the three normal forms?
 In the first normal form tables are divided to
eliminate repeated groups.
 In the second normal form tables are divided so
that no key determines the values of a nonkey
field.
 In the third normal form tables are divided so
that no nonkey field determines the values of
another nonkey field.

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Sequential Accessed Files
In a sequential access file, records can only
be accessed in their predefined sequence.
 An index file is one where an attribute has
been extracted from the records and used to
build a new file whose purpose is to provide
an index to the original file.
 One important type of indexed file is an
indexed-sequential file.

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Indexed Files
An indexed-sequential file is a sequential file
that is stored on a DASD and is both indexed
and physically sorted on the same field.
 These files are frequently referred to as ISAM
files that consists of three distinct areas:
1 The index
2 The prime area
3 The overflow area

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Indexed Files
The index is a map that relates the key fields of
records to their corresponding addresses in the
prime area.
 The prime area is the portion of the disk on which
the actual records are written.
 The overflow area is a separate section of the disk
that is allocated to the file to allow additions to be
made without extensive processing.

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Economic Relations between
Organization Techniques
The basic economics of file processing are
largely determined by the activity ratio.
 What is the activity ratio?
 It is the number of accessed records divided
by the number of records in the file.
 The second economic consideration
concerns response time.

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Economic Relations between
Organization Techniques
What is response time?
 It is the length of time the user must wait
for the system to complete an operation.
 Database management systems (DBMSs)
are computer programs that enable a user to
create and update files, to select and retrieve
data, and to generate various outputs and
reports.

 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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Database Management Systems
and Databases in Practice
All DBMSs contain three common attributes
for managing and organizing data.
 What are these attributes?
1 Data description language (DDL)
2 Data manipulation language (DML)
3 Data query language (DQL)

 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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Database Management Systems
and Databases in Practice
What is a schema?
 It is a synonym for logical data structure
of a database.
 In the absence of integration, each type
of accounting application such as sales,
payroll, and receivables will maintain
separate, independent data files and
computer programs.

 2001 Prentice Hall Business Publishing, Accounting Information Systems, 8/E, Bodnar/Hopwood
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Database Management Concepts
Independent Files
Application One
X
Y
A
B
Application Two
X
Y
C
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D
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