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Data vs. Information
Data:Raw facts. The word raw indicates that the
facts have not been processed to reveal their
meaning.
Information: Information is produced byprocessing raw data.
Information is then used for decision making.
Good decision making is the key to successful
business, therefore the information produced by
data processing should be accurate, relevant and
timely.
Knowledge: The body of information and facts
about a specific subject is called knowledge.
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Data management: Data management is a
discipline that focuses on proper generation ofdata, storage and retrieval of data.
Database
A database is a shared, integrated computer
structure that stores a collection of:
End user data
Metadata
Metadata is data about the data stored in the
database.
E.g. the name of the field, size, data type,
compulsory field or not etc
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Database Management System
Dbms is a collection of programs that manages
the database structure and controls the access to
data stored in the database.
Dbms serves as an intermediary between the user
and the database.
The dbms receives the data requests from theuser/application program and retrieves the data
from the database and sends it back to the user.
Advantages of the dbms
Improved data Sharing
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Several users can have different views of the
same data. Thus data is shared by all
applications
Better data integration
Data is stored at a centralized location. Data
of the entire organization is stored in the
repository.
Minimized data inconsistency
Multiple versions/copies of the same data are
not stored at different locations hence there is
no redundancy of data. And so there is no
inconsistency.
Improved data access
Data stored in the database can be accessed
easily using queries.
Query is a specific request for data storage,retrieval or modification issued by the user to
the dbms.
Improved decision making
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Better managed data and improved data
access make it possible to generate better
quality information, on which betterdecisions are made.
Increased end user productivity
Quick and good decisions increase the
productivity of the employees and in turn the
success of the organization.
Types of databases
Based on the number of users
Single-user database: supports only one user
at a time
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Desktop database: A single user database that
runs on a personal computer
Multi-user database: supports multiple usersat a time
Workgroup database: multi-user database
that supports less then 50 users or a specific
department in an organization
Enterprise database:when the database is
used by the entire organization and supports
many users, across departments
Based on location
Centralized database: a database that
supports data located at a single location
Distributed database: a database that supportsdata located at multiple locations
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Based on type of use
Operational database: a database that is
designed to support a companys day-to-day
operations is called operational database.
It is also known as transactional orproduction database.
Data warehouse: It stores data which can be
used to generate information that is used fortactical and strategic decision making.
Files and File Systems
Earlier organizations used to keep track of the
necessary data using a manual file system.
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The manual file system consisted of files which
were kept in the filing cabinet.
The content of each file was logically related.
E.g. one file would store data related to the
employee another file would store data related to
the customer, products and so on
As the volume of the data increased and thereporting requirements of the organization
increased the manual file system was difficult to
use.
It was time consuming and complicated.
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There fore the need ofcomputer based system
that would track data and produce reports was
created.
Data processing Specialist: created the
computer file structures to store data, created the
software to manage the file structures, and
designed application programs that producedreports based on the file data.
File Terminology
Data: Raw facts
Character: The smallest piece of data that is
recognized by the computer. It requires one byteof storage.
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Field: A character or group of characters that has
a specific meaning.
Record: A logically related set of one or more
fields that describes a person place thing or an
event.
File:A collection of related records
E.g. a file might contain data about customers or
students etc
Computerized file system saved a lot of time and
effort for the users.
It was quick and easy to search for required
information
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Reports could be generated easily and hence
decision making became better.
So each department started making their own
computerized file system and wrote the
application programs to generate reports.
limitations with File System Data
Management
It requires extensive programming
Simple data retrieval tasks require a lot of
programming effort using 3GL languages.
E.g. COBOL, BASIC, C++ and FORTRAN
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It requires the programmer to code what must
be done and how it must be done.
There are no ad hoc query capabilities
There ad hoc queries become impossible with
3 GL languages. It takes very long to
generate such reports a week or a month etc
System Administration can be complex
System administration becomes difficult as
the number of files in the system goes onincreasing
Difficult to change existing structures
Every file requires its own file managementsystem to add modify and delete records and
to view the contents and generate reports.
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Security features are inadequate
Making changes in the file structure requires
changes to be made in the programs that usedata from that file
Security features are limited. Safeguards
designed to protect confidential data aredifficult to program.
Problems with File System
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The limitations of the file system lead to the
following problems:
Structural and Data dependence
A file system has structural dependence i.e.
access to the file is dependent on its structure.
i.e. if the structure changes the programs
which access the data from the file will also
have to be modified.
Structural Independence exists when it is
possible to make changes in the file structure
without affecting the application programs.
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Data Dependence
Even changes in the file data characteristics
affects the data access programs hence the
file system is said to exhibit data dependence.
E.g. If a field in the file changes from integer
to decimal data type then the program
accessing the data will also requiremodifications.
Data independence exists when it is possible
to make changes in the data storage
characteristics without affecting theapplication programs ability to access data.
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Field Definitions and Naming Conventions
The record and field designs in the file
should take into consideration the reporting
requirements.
E.g. Fname, Lname,City, Area code etc
Field names should be descriptive and
meaningful
Length of the field names should be not too
long and not too short.
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It should convey the name of the file and give
an idea about the kind of data that will be
stored in that field.
E.g. Instead of using REN you can use
CUST_RENEW_DATE
There should be a field which uniquelyidentifies the records in the file.
E.g. CUST_ID
Data Redundancy
The data is stored at multiple locations acrossthe organization.
When there is any modification the data
stored at the different locations may not get
updated consistently, thus creating differentversions of the same data. This is known as
data redundancy.
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Uncontrolled data redundancy creates the
following problems:
Data Inconsistency
Data inconsistency exists when different and
conflicting versions of the same data appearin different places.
Reports generated from such data will also be
incorrect.
The data entry errors are more likely when
the same data has to be entered at many
locations. Spelling mistakes, wrong data etc
Data Anomalies
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Anomaly means an abnormality/mistake.
When data redundancy exists there can be
data anomalies because any change in data atone place requires corresponding
modification at all the locations or in all the
files.
A data anomaly develops when all the
required changes in the redundant data are
not made successfully.
Update Anomalies: If the agents phone nochanges it must be changed for every
customer record who the agent serves.
Insertion anomalies: If only customer data
file exists then to add data about a new a
dummy customer entry must be created.
Deletion anomalies: If you delete a customer
record which is the only record that contains
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a particular agent data, then that agents data
will be lost.
Database Systems
Database consists of logically related data
stored in a single logical data repository.
Physical data format: the format in which
the computer stores the data physically on thestorage device.
Logical data format: the format in which
the users view the data. The users may viewthe same data in a variety of different ways.
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There are multiple logical views of the data.
Database System Environment
Database system consists of hardware,
software, people, procedures and data.
Hardware
Hardware is the physical devices of the
system. E.g. computer, printer, routers,
storage devices etc
Software
Operating system manages all the hardware
and software to work together and run thecomputer.
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Dbms software manages the database within
the database system.
Application programs and utilities help to
access the data from the database and
generate reports and perform other tasks.
People
This component includes all the users of the
database system.
System Administrators: see overall
functioning of the system
Database administrators: also known as
DBA-ensure that the database if functioning
properly
Database designers: database architects,
they design the database structure.
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System analysts and programmers: they
design and implement the application
programs. They create the data entry screens,reports and procedures through which users
can access and manipulate databases data.
End-users: users of the system who use the
application programs.
Procedures
Procedures are the instructions and rules
which govern the design and use of the
database system.It specifies the business rules and standards
for input and output data.
Data
A collection of facts stored in the database.
DBMS Functions
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A DBMS performs several functions to
maintain the integrity and consistency of thedata in the database.
All the functions of the dbms are transparent
to the users i.e. the end-users do know cometo know how the dbms carries out such
functions.
The following functions are performed by
dbms
Data dictionary management
The dbms stores definitions of data elements
and their relationships (metadata) in the datadictionary.
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Whenever a program wants to access the data
it sends the request to the dbms, which then
looks up the required data componentstructures and relationships and relieves the
user the task of programming.
Whenever any changes are made in the
database structure, the changes are updated inthe data dictionary also.
Thus the dbms removes data and structural
dependency from the system.
Data storage management
The dbms creates and manages the complex
structures required for data storage thusrelieving you of the task of programming the
complex physical data characteristics.
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Dbms stores data, data validation rules,
procedural code, images and picture formats
also.
Storage management also does performance
tuning: to make data storage and access more
and more efficient and fast.
Dbms stores data in multiple physical files
and can serve multiple users at a time.
Data transformation and presentation
Dbms does the conversion from physical data
format to logical data format and vice versa
during data retrieval and storage respectively.
Security management
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Dbms creates a security system that enforces
user security and data privacy.
Security rules:
Who can access data?
What can be accessed by whom?
What operations can be performed?
Multi-user access control
Dbms allows multiple users can access the
database concurrently.
Dbms uses complex algorithms to provide
multiple users access to the database without
affecting the data integrity and consistency.
Backup and recovery management
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Dbms provides utilities which allow the
DBAs to perform back up and restore
activities on the database.
Recovery management deals with recovery of
data in case of failure of database.
Back up and recovery is needed to preservethe database integrity.
Data integrity management
Dbms enforces data integrity rules, to
minimize data redundancy.
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The data relationships stored in the data
dictionary are used to enforce data integrity.
Data access languages and application
programming interfaces
Dbms provides data access through a query
language.Query language is a non procedural language
one that lets the user specify what must be
done without specifying how it is to be done.
E.g. SQL
Dbms provides administrative tools to the
dbms and also allows programmers to access
data via procedural languages.
Database communication interfaces
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Users can communicate with the databases in
different ways:
Through the internet using browsers orpublishing reports on the website or through
data entry forms etc
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