System Analysis and Design
System Design
- Mr. Ahmad Al-Ghoul
learning Objectives
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Explain data warehousing and
data mining
Differentiate between logical and
physical storage and records
Explain data control measures
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Data Storage and Access
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Data storage and access involve strategic
business tools, such as data warehousing
and data mining software, as well as
logical and physical storage issues,
selection of data storage formats, and
special considerations regarding storage of
data fields
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Data Storage and Access
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Strategic tools for data storage and access
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Data warehousing
A data warehouse is an integrated collection of
data that can support management analysis and
decision making.
 Data warehouses are used to organize information
from many databases for quick and effective
queries
 Data warehouse can link various information
systems and databases
 In the data warehouse, data are organized around
major subjects
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Data Storage and Access
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Strategic tools for data storage and access
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Data warehousing
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Data in the warehouse are stored as summarized rather than
detailed raw data
A data warehouse allows users to specify certain dimensions,
or characteristics
By selecting values for each characteristics, a user can obtain
multidimensional information from the stored data. For
example, in a typical company, suppose that a user wants to
see may 2005 sales results for specific sales rep like sally
brown. The data is stored in two different systems: the sales
information system and human resources information system
Without a data warehouse, it would be difficult for a user to
extract data that spans several information systems and time
frames
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Data Storage and Access
A data warehouse stores data from several systems. By selecting data
dimensions, a user can retrieve specific information without having to
know how or where the data is stored.
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Data Storage and Access
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Strategic tools for data storage and access
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Data Mining
Data mining software looks for meaningful
patterns and relationships among data. For
example, data mining software could help a
consumer products firm identify potential
customers based on their prior purchases.
 The enormous growth in e-commerce has focused
attention on data mining as a tool to analyze Web
visitor behavior and traffic trends
 Data Mining Increase average pages viewed per
session.
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Data Storage and Access
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Strategic tools for data storage and access
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Data mining is a valuable tool for managers who must make
management decisions involving complex issues, because it
can detect patterns and trends in large amount of data
In a recent article in New Architect, a Web-based magazine,
Dan R. Greeing says that “ the great advantage of Web
marketing is that you can measure visitors interactions more
effectively than in brick-and-mortar stores or direct mail. Data
mining works best when you have clear, measurable goals.”
Some of the goals he suggests are:
 Increase number of referred customers
 Reduce clicks to close, which means average number of page
views to accomplish a purchase or obtain desired
information.
 Increase checkouts per visit
 Increase average profit per checkout
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Data Storage and Access
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Logical and Physical Storage
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Logical storage
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Refers to information as seen through a user's
eyes, regardless of how or where that information
is organized or stored.
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A Character is A group of eight bits, or a byte.
A data element, field, or attribute is set of bytes, which is
an individual fact about a person, place, thing, or event.
 A data element, field, or attribute is the smallest
piece of data that has meaning within an information
system.
A logical record contains field values that describe a
single person, place, thing, or event.
Application programs see a logical record as a set of
fields, regardless of how or where the data is stored
physically.
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Data Storage and Access
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Logical and Physical Storage
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Physical storage
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Storage that is strictly hardware-related, because it involves
the process of reading and writing binary data to physical
media such as a hard drive or CD-ROM.
Physical storage involves
 A physical record, or a block, is the smallest unit of data
that is accessed by the operating system.
When the system reads a physical record, it loads the data
from storage into a buffer
 A buffer is a segment of computer memory used for
temporary storage.
The actual number of logical records in a physical record is
determined by the blocking factor
 The blocking factor is the number of logical records in
one physical record.
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Data Storage and Access
A data file consists of physical records, or blocks, that contain logical
records.
You can see that each physical record consists of two logical records that
means the blocking factor is 2
fields
Logical
records
Physical
records
file
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Data Storage and Access
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Data Storage Formats
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Computers use four primary data storage format
 EBCDIC
 EBCDIC, which stands for Extended Binary Coded
Decimal Interchange Code, a data storage method used
on most mainframe computers.
 ASCII
 ASCII, which stands for American Standard Code for
Information Interchange, A data storage method used on
most minicomputers and personal computers.
 Unicode
 Unicode is a relatively recent coding method that
represents characters as integers. Unlike EBCDIC and
ASCII, which use eight bits for each character, Unicode
requires 16 bits per character, which allows it to
represent more than 65,000 unique characters.
 Unicode is important for multinational versions of a
program that will be sold in different countries with
different languages
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Data Storage and Access
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Data Storage Formats
 Binary
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Binary storage format: A format that offers
efficient storage of numeric data.
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Integer format
 A type of binary storage format. The integer format
requires two bytes to store numbers from –32,768 to
32,767.
Long integer format
 A type of binary storage format. The long integer
format can store numbers from –2,147,483,647 to
2,147,483,647 using only four bytes of storage.
Other binary formats exist for efficient storage of
exceedingly long numbers
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Data Storage and Access
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Selecting a Data Storage Format
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In many cases, a user can select a specific data
storage format
You can store documents, spreadsheets, and
databases in Unicode-compatible form by using the
font called Arial Unicode MS
When choosing numeric data formats, you should use
a format that will be adequate for all possible current
and future data
Each data storage format has advantages and
disadvantages
Best answer is it depends on the situation
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Data Control
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File and database control must include all
measures necessary to ensure that data storage
is correct, complete, and secure
A well-designed DBMS must provide built-in
control and security features, including
subschemas, passwords, encryption, audit trail
files, and backup and recovery procedures to
maintain data
Subschema can be used to provide a limited
view of the database to a specific user, or level
of users
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Data Control
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DBMS control and security features
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User ID and Password
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Permissions
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User-specific privileges that determine the type of access a
user has to a database, file, or directory.
Encryption
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A method of limiting access to files and databases to protect
stored data by prove positively that the user is what he/she
claims to be.
A process where data is coded (converted into unreadable
characters) so that only those with the required authorization
can access the data (usually via decoding software).
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Data Control
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DBMS control and security features
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Backup
 The process of saving a series of file or data copies to be
retained for a specified period of time.
Recovery procedures
 Recovery procedures involve restoring data and restarting a
system after an interruption. Recovery procedures can be
used to restore a file or database to its current state at the
time of the last backup.
Audit log files
 Audit log files record details of all accesses and changes to a
file or database and can be used to recover changes made
since the last backup.
Audit fields
 Audit fields are special fields within data records to provide
additional control or security information. Typical audit fields
include the date the record was created or modified, the
name of the user who performed the action, and the number
of times the record has been accessed.
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Sequence Summary
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Data warehouse can link various information systems and databases
In the data warehouse, data are organized around major subjects
Data warehouse allow easy access via data mining software, that
searches for patterns and identifies relationships not imagined
human decision makers
Data mining software looks for meaningful patterns and
relationships among data
Logical storage is information seen through a user’s eyes, regardless
of how or where that information actually is organized or stored.
Physical storage is hardware-related and involves reading and
writing blocks of binary data to physical media
A logical record is a related set of field values that describes a single
person, place, thing, or event
A physical record consists of one or more logical records, depending
on the blocking factor
Data storage formats include EBCDIC, ASCII, Unicode, and binary
File and database control measures include limiting access to the
data, data encryption, backup/recovery procedures, audit-trail files,
and internal audit fields
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Sequence Summary
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In this Sequence we have
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Explained Strategic tools for data storage and
access including data warehousing and data
mining
Differentiated between logical and physical
storage and records
Explained the various types of data storage
formats
Explained how to Select a Data Storage
Format
Explained data control measures
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Reference
[1] System Analysis and Design, Sixth
Edition
Authors: Gary B. Shelly, Thomas J.
Cashman and Harry J. Rosenblatt
Publisher: SHELLY CASHMAN SEWIES.
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