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A brief idea about management

Management as defined by Mary Follett is "the art of getting things done through

people". A manager is defined as a person who achieves the organizations goals bymotivating others to performnot by performing himself. Management comprisesthe process of planning, organizing, staffing, directing, coordinating and controllingthe efforts of the members of the organization to achieve common stated goals of theorganization. hether management is an art or a science is a very sub!ective uestion.#ut it can be said without doubt that modern management in the environment oftechnology is becoming more of a science than an art.

$n the process of management, a manager uses human s%ills, financial resources,technological resources, natural resources and scientific methods to perform all theactivities leading to the achievement of goals.

&he management process involves a continuous resolution of conflicts of one %ind orthe other which affects the achievement of goals. $n the management of any activity, amanager comes across human conflict, conflict of goals, conflict between alternativeresources, conflict of time, conflict of approach or method and the conflict of choice.&he manager uses a variety of tools, techniues and s%ills while e'ecuting themanagement process of planning, organizing, staffing, coordinating and controlling.

Functions of the ManagerAn individual who gets the things done is a Manager. $t is necessary to distinguishbetween the tas%s and the functions. hile managing, a manager may perform the

individual tas%s such as accounting, selling, manufacturing, purchasing, etc. &heseactivities are called as tas%s and not as functions. Managers have the followingfunction(

)* Focuses on efficiency+* ees that the organization is doing things right-* Authorizes and approves all resources reuired for success* /etermines, models, and enforces behavioral changes0* Appoints effective change agents to manage implementation details1* /evelops meaningful, achievable, measurable goals and ob!ectives2* 3nsures implementation approach is realistic

4* Monitors progress5* Approves mid6course corrections3tc.

Processes executed by managers

&he processes that are e'ecuted through the managerial functions are 7lanning,8rganizing, taffing, /irecting, 9oordinating and 9ontrolling.

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1. Planning-7lanning is basic to all managerial functions. $t determines the goals andob!ectives. $t is a process of selecting one course of action, from different alternatives,for achieving the stated goals, ob!ectives and targets. $t is a decision ma%ing processdetermining in advance what to do, how to do, when to do and who is to do. 7lanningcreates a frame of activity and events which are to happen or a runway for achieving

corporate goals, ob!ectives and targets. 7lanning process demands resource allocationthrough decision6ma%ing. &he organization may have a plan: but uestion is howefficient ; effective the plan is. &he efficiency of a plan is measured by the amount itcontributes towards achievement of goals. &he plan is efficient if it achieves the goalswith less investment or with fewer resources. &herefore, efficient planning involvesselecting a plan among several alternative plans. An efficient plan enables themanagement to handle uncertainty and ris% in the business. $t helps to handle thechange occurring in the environment and affecting the plan itself. 7lanning helps toma%e operations economical as it continuously evaluates the costs and outputs andforces optimum use of resources. $t further helps to control business operations at alllevels with common reference to goals, ob!ectives and targets.

2.Organizing -8rganizing, in companys point of view, is the management functionthat usually follows after planning. $t involves evolving the structure of the peoplewor%ing in the organization and their roles. $t deals with a uantitative and aualitative aspect of manpower in terms of placement, the roles they play and therelations amongst them, with the aim that they wor% together effectively towardsaccomplishing the goals, ob!ectives and the targets of the organization. $n essence, itdeals with organizing the manpower resources for a given plan of e'ecution.

. !taffing- the function taffing deals with manning the enterprise as per theorganization structure so that they together implement the process of management. $treuires defining the manpower needs per position or center of activity. taffinginvolves not only selection of persons but also their appraisal and development so thatthey can perform their designated roles. &he selection of a person is a difficult tas%.taffing of enterprise should be for todays needs, as well as that of future.

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$. %oordinating- coordinating is the function, which brings a harmony andsmoothness in the various group activities and individual efforts directed towards theaccomplishment of goals. $t is a process of synchronizing individual actions and theefforts which may differ because of the differences in the personal goals and thecommon goals, the differences in the interpretation of methods and directions. $t is,

therefore, necessary to underta%e centrally a process of coordinating and reconcilingthe differences in the approach, timing, efforts and interests towards a common goal.&his tas% is to be carried out by the authority placed at a higher level in theorganization structure.

&. %ontrolling-the last but most important step in the process management iscontrolling, for the successful e'ecution of management plan. ithout control, theprocess becomes unproductive. &he purpose of the control is to regulate the processin such a way that the process continuously strives for the achievement of the goals,ob!ectives and targets. 9ontrolling is a process of measurement of an output,comparing it with the goals, the ob!ectives and the target, and ta%ing corrective

actions, if the output is falling short of the standard norms. 9ontrolling ensures anachievement of the plan. &he essence of the control lies in good planning. $t helps toevaluate the performance, highlights abnormal deviations, and guides a manager tota%e specific corrective actions. &his may call for a change of plan, a reallocation ofresources, a modification of methods, procedures and even the organization structure.&he control is central to the managerial function.

&he manager=s main function, therefore, is planning and control of the businessfunctions and operations. hile performing these functions, he resorts to thescientific approach to the management.

'se of %om(uters For Managerial A((lications

Followings are a few e'amples of $ndustry egments where computer is used inmanagerial application.

). Manufacturing+. #an%ing ; Finance-. .$nsurance. tility ervice

1. 3ducation2. &ransport4. 7rofessional ervice5. ?etail ervice)@. /istribution

&he use of computer for managerial application in any industry segment can be dividedinto #asic ; Advanced evel.

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Manufacturing

#asic evel Advanced evel

). Accounting ). Forecasting

+. 8rder 7rocessing +.9omputer Aided Manufacturing

-. 7rocurement -. #udgeting

. $nventory 9ontrol . 9omputer Aided /esign

0. Mar%eting 0. Manufacturing ?esource 7lanning

1. Buality 9ontrol

)an*ing + Finance


). Managing avings Account ). Automated &eller Machine

+. 9hec% 7rocessing +. 7ortfolio Analysis

-.Money &ransfer -. 9ash Flow Analysis

.9ost 9ontrol .9entralized File ystem

,nsurance


). 7remium 9alculation ). ?is% Analysis

+. 9ustomer #illing +. 7olicy Approach

-. #onus 9alculation -. $nvestment Analysis

. Forfeiture 9alculation . 9ash Flow Analysis

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0. Agent 9ommission 0. Cew #usiness /evelopment

ealth %are


). #illing ). 8.&. cheduling

+. $nventory 9ontrol +. $ntensive 9are unit scheduling

-. Accounting -. /iagnostic aboratory automation

. 7atient

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0rans(ort


). 9ost 9ontrol ). &raffic 7attern analysis

+. ?ate calculation +. Automatic rating

-. Accounting -. ?eservations

. Maintenance and cheduling

Professional !erice

#asic evel Advanced evel). Accounting ). 9redit 9hec%ing

+. 9ustomer ?ecord +. /ata #ase Management

-. &as% preparation -. &echnical Analysis

etail !erice


). 9ustomer #illing ).ust $n &ime

+. Accounting +.3lectronics /ata &echnologies

-. ells Analysis -. 7oint 8f ale

. $nventory ?eport . ells Forecasting

0. Merchandising

#istribution


). 8rder 7rocessing ). ells Forecasting

+. 7urchasing +. Merchandising

-. arehouse 9ontrol -. Gehicle chedule

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. $nventory 9ontrol . ogistics

,nformation %once(ts

$nformation is a %ey resource used at every level of business organization. $n recent yearssome specific trends have emerged, resulting into increased importance for informationas a %ey resource.

&he increasing comple'ity of the modern society in general and business in

particular is the first trend.

8rganizations are becoming larger. Many organizations today have global or internationalpresence. &he functioning of the organizations is becoming comple'. More comple'organization, more importance of information is felt.

&he second trend is the rapid progress in the field of information technology.

9onstant improvement in computing power with a downward trend in costs of computingis providing wider applications for information technology in business.

&he6increasing awareness of scientific management principles is another trend.

&he scientific approach of planning, controlling and decision ma%ing is resulting intoincreasing awareness about the need for information and its application in managementprocess.

hat is #ata3&he word datum means raw fact. &he word data is plural of datum referring to more thanone fact. $n practice, however, people use data as both the singular and plural form of theword./ata can e'ist in a variety of forms 66 as numbers or te't on pieces of paper, as bits and

bytes stored in electronic memory, or as facts stored in a person=s mind.

hat is ,nformation3

hen data is organized in useful form it is considered as information. /ata is theraw material. &he finished product is information. $nformation is a collection of

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meaningful and relevant data that describe events and entities. hen data is arranged in ameaningful manner, it is said that data has been converted into information.

H#istinguish bet4een #ata and ,nformation

#ata ,nformation

/ata is raw fact. $nformation is ripe./ata cant be understood or made useby the users.

$nformation is understood and used by theusers.

/ata has no meaning of itself, i.e., ithas no significance beyond itse'istence.

$nformation has been given meaning by way ofrelational connection. &his "meaning" can beuseful, but does not have to be.

/ata is unprocessed information. $t isgenerally disorganized anddisintegrated in the form.

hen data are processed, organized, structuredor presented in a given conte't so as to ma%ethem useful, they are called $nformation. ecan say information is processed data.

/ata doesnt depend upon information. $nformation is based upon and derived from

data.3'ample)6 My goals this season 6), ), +, -, ), @, +, @, +, ), -, ), ), +, -, ,), -, 2, , ), +6 is a set of numbers, i.e.,data. $t is not useful.

3'ample)6$f $ process the data of left column, $can sayAverage I +.@um I 0

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&he term information is generally used in imprecise manner. &he borderline between dataand information is difficult to define. $t can be said that one person=s information may beanother person=s data. At times, the information for one level in the organization is datafor the other level in the organization. At times information, which is an output of a givendata processing, activity is input for further data processing activity that produces

information. &here could be a series of such output as input situations.

3'ample( 6 hen the district administration sends information about the crops and theircurrent status to national body, it is information at district level but data at the nationallevel. &he term information can be considered to mean processed data in a meaningfulform for the user, which has an application or specific usage value.

3'ample( 6$n the same sales analysis e'ample, the first dataprocessing activity may be using salesinvoices as input and producing product wise sales statement as the output.&he product wise sales statement along with the product wise sales target are processed inthe second stage of data processing to produce sales variance report as the output.

&his sales variance output comparing sales targets and actual sales is input for thedecision support system, which the manager uses for decision6ma%ing.

hat is #ata (rocessing3

&he process of converting data into information is often termed as data processing. &heob!ective of data processing activities is to convert raw data into meaningful informationthat can be put to use. /ata 7rocessing is a value added process since it adds value touseless data to convert it valuable information.$n data processing

)* /ata is arranged, manipulated, organized+* $ts content is analyzed and evaluated-* $t is placed in a proper conte't for human users.

$nformation is the finished product of the data processing 6 is useful only when it is put touse in decision ma%ing, planning controlling etc.

Processing Model

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$n the above diagram in JA* shows that the data captured is used as input for theprocessing activity. &he input is processed to produce output for generation of meaningfulinformation.

&he diagram in J#* shows that in a business data processing activity, the dispatch data isused as input to produce invoice, which is the output of processing activity.

H%lassification of information

&he information can be classified in a number of ways to provide a better understanding.uch as(

15 Action ersus 6o-action information- &he information, which induces action, iscalled action information. &he information, which communicates only the status of a

situation, is no6action information. KCo stoc%= reports calling a purchase action is anaction information but the stoc% ledger showing the store transactions and the stoc%balances is a no6action information.

25 ecurring ersus non-recurring information- &he information generated at regularintervals is a recurring information. &he monthly sales reports, the stoc% statements etc.are recurring information. &he information doesn=t generated at regular intervals is a non6recurring information. &he financial report on the mar%et research study is non6recurringinformation.

5 ,nternal ersus external information- &he information generated through the

internal sources of the organization is termed as an internal information, while theinformation generated through the Eovernment reports, the industry surveys, etc. istermed as an e'ternal information, as the sources of the data are outside the organization.

"5 0he information can also be classified as under7 in terms of a((lication.

Planning information

9ertain standards, norms and specifications are used in the planning of an activity.

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H%ost of ,nformation

$t may include(Ja* 9ost of acuiring data,Jb* 9ost of maintaining data,Jc* 9ost of generating information, and

Jd* 9ost of communicating information

H9alue of ,nformation

$nformation plays a very important role in business organizations. mooth flow andproper utilization of information is essential for the very e'istence of the organization.$nformation by itself does not have a value attribute. &he value is gained throughappropriate use of the information in specific activities.

$nformation is a %ey input in decision6ma%ing activity. $f incorrect or incomplete

information is used as the basis for decision6ma%ing, the resultant decision itself will bedoubtful. &heoretically, value of information is considered to be the value of the changein decision behavior resulted by the information less the cost of obtaining theinformation. &he mathematical model of computing the value of information in decision6ma%ing assigns the value in each decision behavior and the cost of obtaining theinformation. hen new information results in a different decision, value of such changein decision behavior is obtained by subtracting the value of previous decision from thenew decision. $f the new information does not result in a new decision the value ofinformation is considered to be nil.

&here are various attributes of $nformation that increase the value of information that is

generated through the data processing. ome of the important attributes are(

o Accuracy and degree of precision

o Authenticity

o 7resentation format

o cope of 9overage

o Freuency of updates

o $nformation ources

o &ime span coverage

o 9ontent 9overage

o

Adeuacy

$n addition to decision6ma%ing, information plays an important role in activities such asplanning, control, coordination, motivation etc. &he value of information in suchapplication areas may not necessarily be uantified.

&he value of information in planning is manifested through the degree of correctness inforecasting the future events, realistic estimations, success probability etc. $n case of

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control activities the manifestation is in terms of response time for feedbac% control loopcompletion, accuracy of measurement etc.

H:uality of ,nformation

Buality of information is very important in a business organization. &he term uality isdefined as "conformance to the reuirements".

$nformation is used in a variety of applications. $t is used for planning, controlling,motivating, staffing, coordinating, decision6ma%ing etc. 3ach of these activities has acertain set of reuirements about the information. $f the information produced meetsthese reuirements, the information can be considered as uality information. $f theinformation used is not of the right uality, it is bound to adversely affect the actionsbased on such information.

&he content of information is normally a %ey element of the uality reuirements. Buality

information provides relevant information without creating a data overload and withoutgenerating unwanted information. &oo much of information can cause diversion ofattention resulting into overloo%ing of vital issues. $nformation content should properlyorganized eliminates the ris% of overloo%ing the vital issues. $t should direct the attentiontowards %ey elements of information that are actionable.

&he presentation of the information and degree of detailing is another %ey element of theuality reuirements. hen the information is aimed at operational level of managementthe degree of detailing may be necessary. hen the information is aimed at tactical orstrategic levels the same degree of detailing may not be necessary.

,nformation /ffectieness Parameters

$nformation can be identified by effectiveness parameters. &he degree of importance foreach of these parameters would vary depending on organizational and environmentalfactors. &he information parameters are as follows(

Accuracy-

&he information that is provided for Manager=s to ma%e decision must be sufficientlyaccurate.

0iming-

&he information must be communicated to the actual user of the information atappropriate time.

%ontents-

&he contents of information must be appropriate to meet the >ser reuirements.>nwanted information must be eliminated to avoid "$nformation 8verload leading toconfusion.

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'nderstanding-

&he actual users should easily understand the information that is provided. &he simplicityof understanding is essential for effective usage of information.

A((lication-

&he information should be designed based on the end application to which theinformation is being put. $f the information is being used to base critical businessdecisions, then the content, timing and accuracy reuirements would be different than theinformation which is being used for reference or routine control purposes.

Fre;uency-

&he freuency at which information updates are to be provided should be in line with theusage of information or the time cycle of the activity. For e'ample the information that isused for ma%ing decisions about monthly production plan need not be updated on a dailybasis.

%ommunication-For effective use, information must be communicated from the source to the destination.

!ources of ,nformation

$nformation is obtained from different sources in a business organization.&he sources of information can be classified by their nature, namely: $nternal ande'ternal.

/xternal !ources of ,nformation

&he3'ternal information sources are typically related to the environment in which thebusiness organizations function. $n practice the e'ternal sources of information includeEovernment, trade organizations, published information, newspapers, news agencies,ban%s and financial institutes, customers and suppliers, mar%et research agencies etc.

,nternal !ources of ,nformation

&he internal sources of information include the functional or departmental dataprocessing activities. &hese activities produce information, which is used at operational,tactical as well as strategic levels in the organization. ithin organization information isgenerated through reports.3'amples( 6

a* A field salesperson prepares the daily report. &his reports provides the informationabout the number of calls made, total sales, collection etc.b* &he budgetary control report provides information about the budget amount and actuale'penditures.

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&he hierarchical structure of an organization may have several levels. &he entire structureconsisting of a number of levels can be grouped in three layers. &hey are(

&op management

Middle management

8perational level management

&he roles and responsibilities of these three levels are different, so are their informationneeds.

&op management is involved in strategic activities, policy ma%ing and goal

setting. &hey need information support that helps in carrying out strategic levelactivities. &he information reuirement for these activities is future oriented andinvolves e'ternal sources. &he information presentation is at abstract level and theaccuracy reuirement is moderate.

&he middle management involved in tactical activities. &hey need information

support for tactical level. &he information reuirement at this level involveshistorical analysis and future trends and involves both internal and e'ternalsources. &he information presentation focus shifts from abstract to more elaborateand the degree of accuracy increases.

&he operating level=s management information needs are oriented towards day6to6

day management of operations. &he operational level information reuirement ismainly from internal sources. &he information presentation is elaborate with ahigh degree of accuracy.

0y(es of ,nformation&he information can be considered as strategic, tactical and operational information basedon the receiver and user of the information. 8n the basis of this classification there arethree types of information.

trategic information

&actical information

8perational information

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Figure 1 - Pictorial re(resentation of

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O(erational ,nformation&he operational information, as the name suggests, deals with specific operation withinan organization. &he operational information is often produced as a result of dataprocessing activity. pecific users, often limited in numbers are users of the operational

information. &he operational information is more specific than other types of information.

ome of the more common e'amples of operational information are daily attendancereport, pending purchase orders statement, item wise stoc%s held, wor% in progress, shiftreports etc. &his operational information is used as a data for further processing to obtaintactical information.

hat is information (yramid3

7yramid is a structure which starts from a point and then increase step by step

towards a broad base. /ifferent types of information needed by an organization canalso be represented using a pyramid structure. For the representation purpose we canpartition the pyramid structure into three portions. e can represent operationalinformation using the bottom portion of the pyramid since volume of operationalinformation is large and also because representation of operational information iselaborate. 8perational level manager who will actually use this type information arealso large in number. &hen we can represent tactical information using the middleportion of the pyramid since the volume of tactical information is less thanoperational information and it is more abstract in form than operational information.&he middle level managers who use tactical information, are also few in numbercompared to operational level managers. trategic information can be representedusing top portion of pyramid, because it is very small in volume compare to other twotypes of information also it is also more abstract in form compared to tacticalinformation. >ser of strategic information that is number of top level manager is alsovery few compared to middle level managers.

Picture of ,nformation Pyramid

&op evel Managers

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A few solved e'amples O

/xam(le 1 = Proide a list of (ossible strategic7 tactical and o(erational

information needs for uniersity7 restaurants and chemical (lants

olution(

'niersity

trategic

i* ob prospect in respect of newPe'isting professional ; academic coursesii* $nformation about grant from government or publiciii* Audit results of different departmentsiv* &he latest trend in educationv*

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&acticali* ?oom decoration ; food items that able to draw customers attentionii* 9ustomer demand for new itemsiii* 9ustomer complaints about food or service ualityiv* 9ustomer complaints about desired item unavailability

v* eather waiter maintainsP violates /iscipline and uniform

8perational

i* Already Fulfilled order ; pending ordersii* 9ustomer reception styleiii* Art of conversation with Euestiv* &odays menu and available foods items at every momentv* 9ustomer billvi* toc% of suppliesvii* ?euired $tems need to be procured everyday

%hemical Planttrategic

i* 7ollution control law of governmentii* trategy applied by other plants to control pollutioniii* Availability of new techniue and tools, which can be used in transformation

and or separation of materialsiv* Cew research and development in this fieldv* Annual production and sales summary

vi* #uying habits of potential customervii* Audit reportviii* Cew idea to test percentage of chemicals in finished products

&actical

i* ?aw material procurement procedureii* ?euirement of $ndividual customers and strategy applied to provide

customized productiii* Freuently received customer complaintsiv* Buality control of finished product

8perational

i* $nventory statusii* /ay6to6 day production plant reportiii* $nbound and outbound logistic operationiv* /ay6to6day ales report

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/xam(le 2 - >reat !urgers is a (o(ular first food chain in ,ndia7 mainly sell meat-

based fast food. !ince egetarian moement is getting stronger and fish is gaining

(o(ularity as ?brain food@7 the to( management decided to add egetarian and fish

based items to the current menu. Proide a list of (ossible decisions ta*en bymanagers at different leels

!olution -

#ecision made by o(erational leel managementFirst operational level managers, generally who are attached to any one retail shops %eepstrac% of following(

)* /aily sales of meat based items+* /aily demands of vegetable and fish based items-* &he number of vegetarian leave shop for unavailability of vegetable items* Cumber of customers agree to accept meat based food instead of vegetable and

fish based foods0* 3conomic condition and Food habits of local customers

&hen they should send all the above information to the middle level managers.

#ecision made by middle leel management

First middle level managers, generally who are responsible for proper management at aparticular area summarizes the information received from low6level managers.

&hey calculate the area wise sales of meat6based foods: area wise demand for vegetarianand fish based products, number of unsatisfied customers etc. &hen they pass thesereports to the top6level management.

#ecision made by 0o(-leel Management

&op6level management who are generally responsible for strategic decision considers anumbers of e'ternal and internal information.

3'ternal information for e'ample food offering by competitive food chains, number ofcustomers prefer competitors product because they provide varieties of items. &hen9hoice of local peoples and their economic conditions of local people also need to beconsidered by them. Ce't as internal information they should consider summarized areaor region wise sales of meat based items and demand for fish or vegetable items

&hen they may decide to introduce vegetarian and fish based food. &hey may decide tointroduce it through all over country or in some selected regions depending on demand.&hey may decide to %eep menu of meat base items unchanged or change it depending onsales history.

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8rganizing /ata and $nformation

/ata are vital organizational resources that need to be managed li%e other importantbusiness assets. &hat=s why organizations and their managers need to practice dataresource management.

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/atabase6A collection of integrated and related files

File6A collection of related records

?ecord6A collection of related fields

Field6A group of characters

9haracter6#asic building bloc% of information, represented by a byte

hat is database3A database is an organized collection of interrelated information Jwhich is relevant for anenterprise*, to meet users needs.

hat are the desirable (ro(erties of database3

1. %ontrolled edundancy?edundant data occupies space and therefore, is wasteful. $talso degrades performance. $f versions of the same data are in different phases of

updating, the system often gives conflicting information. A desirable aspect of databasedesign is storing data only once, which controls redundancy and improves systemperformance.2. /ase of

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C ecoery from Failure&he system must recover uic%ly after it is down with no lossof transactions. &his ob!ective also helps maintain data accuracy and integrity.D. Performance&his property emphasizes response time to inuiries must be suitable tothe use of the data.

0y(es of #atabases

i' ma!or types of databases that may be found in computer6using organizations are asfollows(O(erational#atabase

Analytical#atabase

#ataarehouse

#atabase

#istributed#atabase

/nd-'ser#atabase

/xternal#atabase

&hesedatabasesstoredetailed dataneeded tosupport theoperationsof the entireorganization. 3'amples

are customerdatabase,personneldatabase,inventorydatabase andotherdatabasecontainingdatagenerated by

businessoperations.

&hesedatabasesstore data andinformatione'tractedfrom selectedoperationaland e'ternaldatabases.&hey consist

ofsummarizeddata andinformationmost neededby anorganizations managers.

A datawarehousestores datafrom currentand previousyears thathas beene'tractedfrom thevarious

operationalandmanagementdatabases ofanorganization. $t is acentralsource ofdata that hasbeen

standardizedandintegrated soit can beused bymanagersand otherend user

&hese aredatabases oflocal wor%groups anddepartmentsat regionaloffices,branchoffices,manufacturin

g plants, andother wor%sites. &hesedatabases canincludesegments ofboth commonoperationaland commonuserdatabases, as

well as datagenerated andused only at auser=s ownsite.

&hesedatabasesconsist of avariety ofdata filesdevelopedby end usersat theirwor%stations.

Access toe'ternalonlinedatabasesor databan%s isavailablefor a feefromcommercia

linformation services,or withoutchargefrom manysources ontheinternet.

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professionals throughoutanorganization.

/xam(le of databases -3lectronic filing system is an e'ample of traditional databasesystem.$n &he traditional file system, separate files are created and stored for each applicationprogram.

#ra4bac*s

Of File system

#ata redundancy and inconsistency6ince different programmers create the

files and application programs over a long period. ame information may beduplicated in several places Jfiles*./uplication of data in separate files leads tohigher storage and access costs. $n addition it may leads to data inconsistency thatis various copies of the same data may no longer agree.

#ifficulty in accessing data- &he point here is that conventional file6processing

environments do not allow needed data to be retrieved in a convenient and

7ayroll

$nventory

$nvoicing

Managementinuiries

7ayroll programs

$nvoicing programs

$nventory control programs

Management inuiriesprograms

?eports

?eports

?eports

?eports

Files 'sersA((lications (rogram

Figure 2 = 0raditional File !ystem

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efficient manner. #ecause whenever a new information need is generated, a newapplication program needs to be written.

#ata isolation-because data are scattered in various files, and files may be in

different formats, writing new application programs to retrieve the appropriate

data is difficult.

,ntegrity (roblems-the data values stored in the database must satisfy certain

types of consistency constraints. /evelopers enforce these constraints in thesystem by adding appropriate code in the various application programs.

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Figure = #atabase Management !ystem

ho is #)A38ne of the main reasons for using /#Ms is to have central control of both the data andthe programs that access those data. A person who has such central control over the/atabase Management system is called a database administrator J/#A*.

Adantages of #atabase Management !ystem in a business information system

ithout a database management system organizing, controlling and cataloging data, aninformation system would be an unorganized conglomeration of data. &he advantagesprovided by /#M are as follows(

). %ataloging of File !tructures - 0heprocess of cataloging files in a databasemanagement system J/#M* is e'tremely important. ithout the process of a filestructure, files would be hard to access and operate. A file structure within aJ/#M* provides an orderly structure for file access and management.

+. eduction of edundancies -9entralized control of data by the /#A J/atabase Administrator* avoids unnecessary duplication of data and thus effectivelyreduces the total amount of data storage reuired, also eliminates the e'traprocessing ; the inconsistencies that tend to be present in redundant data files.

-. !haring #ata -A /#M allows the sharing of data by any number ofapplication programs or users

. #ata ,ntegrity -9entralized control can also ensure that adeuate chec%s areincorporated in the /#M to provide data integrity. /ata integrity means that thedata contained in the database is both accurate and consistent. &herefore, datavalues being entered for storage could be chec%ed to ensure that they fall within aspecified range and are of the correct format. For e'ample, the value for the ageof an employee may be in the range of )4 to 1@.

0. !ecurity 6 unauthorized persons must not access confidential data. /ifferentlevels of security could be implemented by /#M for various types of data and

$nvoicingprograms

$nventorycontrolprograms

Managementinuiries

programs

?eports

?eports

?eports

7ayroll /ata

$nventory /ata

$nvoicing /ata

8ther /ata

/atabaseManagement

ystem

?eports7ayrollprograms

7hysical /atabase $nterfaceApplication programs

>sers

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operations.1. #ata ,nde(endence -0he files may migrate from one type of physical media to

another or the file structure may change without any need for changes in theapplication programs. Application programs need not be changed even if fieldsare added to an e'isting record: nor do they have to be changed if fields not used

by application programs are deleted.2. educed Programming %osts7 educed #eelo(ment and ,m(lementation0ime7 educed File Maintenance %osts -#ecause many of the $nputPoutputJfile definition and file maintenance* routines normally coded by the programmersare now handled through the data base management system, the amount of timeand money spent writing an application program is reduced. /atabasemanagement systems reduce file Maintenance 9osts by performing filemaintenance in a more convenient and more efficient manner.

#isadantage of #atabase Management !ystem

). A significant disadvantage of the /#M system is cost. $n addition to the cost ofpurchasing or developing the software, the hardware has to be upgraded to allowfor the e'tensive programs and the wor%spaces also reuired for their 7rograme'ecution and storage

+. &he lac% of duplication reuires that the database be adeuately bac%ed6up so thatin the case of failure the data can be recovered.

-. &he data is accessible from a single source namely the database. &his increasesthe potential severity of security brea%s. ingle source of data increases disruptionof the operation of the organization because of downtimes and failures.

hat is schema-3 chema is logical database description i.e., overall chart of all the

data item types and record6types stored in database.

An e'ample Rales /atabase

&able6 )( 9lientSmaster R >sed to store client information9lientSnumber Came Address 9ity 7incode tate #alanceSdue

&able6 +( 7roductSmaster R >sed to store product information7roductSnumber

/escription

>nitSmeasure

BuantityS8nShand

?eorderSlvl

ellSprice

9ostSprice

&able6 -( alesmanSmaster R >sed to store information about salesman wor%ing in acompanyalesmanSnumber Came Address 9ity 7incode tate alSamt &gtStoSget ActualSsales ?emar%s

&able6 ( alesSorder6 >sed to store 9lients order8rderSnumber 8rderSdate 9lientSnumber /elySaddress alesmanSnumber /elyStype #illedS$n /elySdate 8rder

&able6 0( alesSorderSdetails table8rderSnumber 7roductSnumber BtyS8rdered BtySdisp 7roductSrate

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hat is #ata #ictionary3

/ata dictionary is a part of /#M. $t is used to manage metadatathat is, data thatdescribes the database structure, constraints, authorizations, and so on. A useful datadictionary system should store and manage the following types of information(

/escriptions of the schemas of the database system /etailed information on physical database design

/escriptions of the database users, their responsibilities, and their access rights

sage statistics such as freuencies of ueries and transactions and access counts

to different portions of the database

#atabase

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finished e'ecution before &i started, or &! started e'ecution after &ifinished. &hus, eachtransaction is unaware of other transactions e'ecuting concurrently in the system.#urability-After a transaction completes successfully, the changes it has made to thedatabase persist, even if there are system failures.

&hese properties are often called the A9$/ properties: the acronym is derived from thefirst letter of each of the four properties.

hat is #ata Model3 6>nderlying the structure of a database is the data model. #y structure of a database wemean the data types, relationships, and constraints that should hold on the data.

%ategories of #ata Models-

igh-leel or conce(tual data models6 7rovides concepts that are close to theway many users perceive data.

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&he ne't step in database design is the actual implementation of the database, using acommercial /#M. o the conceptual schema is transformed from the high6level datamodel into the implementation data model. &his step is called logical design.

!te(

Finally, the last step is the physical design phase, during which the internal storagestructures, access paths, and file organizations for the database files are specified.

/ntity-relationshi( E/-5 Model63ntity6relationship J36?* Model6 &he 3ntity6relationship J36?* Model is a high6level orconceptual data model. $t is based on a perception of a real world that consists of acollection of basic ob!ects, called entities, and or relationship among these ob!ects. &he36? model employs three basic notations( entity set, relationship sets and attributes.

i* /ntity !ets-An entity is a thing or ob!ect in a real world that is distinguishablefrom all other ob!ects. An entity set is a set of entities of the same type that

share the same properties or attributes. &he set of all persons who arecustomers at a given ban%, for e'ample can be defined as the entity setcustomer.

ii* Attributes6An entity is represented by a set of attributes. Attributes aredescriptive properties possessed by each member of an entity set. 7ossibleattributes for customer entity set are customer6id, customer6name etc.

iii* elationshi( !ets-A relationship is an association among several entities. Arelationship set is a set of relationships of the same type. For e'ample we candefine a relationship #orrow that associates customer entity and oan entity.

uppose that ?am and 6)0 are two entities. ?elationship #orrow associates ?am withloan 6)0. &his relationship identifies that ?am is a customer with loan number 6)0.

Ma((ing cardinalities69ardinalities of entity set A, e'press the number of instances ofentity set # that may be associated with each instance of entity set A.

For a binary relationship set ? between entity sets A and #, the mapping cardinality mustbe one of the following(

One to one6an entity in A is associated with at most one entity in #, and an entity in # isassociated with at most one entity in A.One to many6 an entity in A is associated with any number Jzero or more* of entities in#. An entity in #, however, can be associated with at most one entity in A.Many to one6 an entity in A is associated with at most one entity in #. An entity in #,however, can be associated with any number Jzero or more* of entities in A.Many to many-An entity in A is associated with any number Jzero or more* of entities in#, and an entity in # is associated with any number Jzero or more* of entities in A.

/ntity-elationshi( #iagram - 36? diagram represents entity sets, its attributes andrelationship sets graphically, i.e., 36? diagram can e'press the overall 9onceptualstructure of a database graphically.

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&his diagram is simple and clear.

ome notation of 3? /iagram

?ectangles, which represent entity sets

3llipses, which represent attributes

/iamonds, which represent relationship sets ines, which lin% attributes to entity sets and entity sets to relationship sets

$f 3) ; 3+ are two entity sets and ? is relationship set. &hen a directed line from therelationship set ? to entity set 3+ specifies relationship is one6to6one or many6to6onefrom 3) to 3+. An undirected line from the relationship set ? to entity set 3+ specifies the? is either many6to6many or one6to6many relationship set from 3) to 3+.

An exam(le to illustrate /- #iagram

9onsider the entity6relationship diagram in Figure , which consists of two entity sets,customer and loan, related through a binary relationship set borrow. &he attributesassociated with customer are customer6id, customer6name, customer6street, and customer6city. &he attributes associated with loan are loan6number and amount. Attributes of anentity set that are members of the primary %ey must be underlined. &he relationship setborrower may be many6to6many, one6to6many, many6to6one, or one6to6one.

$n figure .A relationship set borrower is one6to6one from customer to loan$n figure .# relationship set borrower is one6to6many from customer to loan

$n figure .9 relationship set borrower is many6to6one from customer to loan$n figure ./ relationship set borrower is many6to6many from customer to loan

9ustomers oans#orrow

customerSid customerSname

customerSstreet customerScity

loanSnumber amount

oans#orrow

customerSid customerSname

loanSnumber amount

".A

Figure "

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3ach child record type can have only one parent record type: thus an M( C

relationship cannot be directly e'pressed between two record types. 8nly)( Crelationship between record types is possible.

/ata in a parent record applies to all its children records

A child record occurrence must have a parent record occurrence: deleting a parent

record occurrence reuires deleting its entire children record occurrence.

3'ample, an organization might store information about an employee, such as name,employee number, department, and salary. &he organization might also store informationabout an employee=s children, such as name and date of birth.

&he employee and children data forms a hierarchy, where the employee data representsthe parent segment and the children data represents the child segment. $f an employee hasthree children, then there would be three child segments associated with one employeesegment.

9onsider a database that represents a customer6account relationship in a ban%ing system.&here are two record types( customer and account. 9ustomer record has fields6 customer6name, customer6street, customer6city. Account records have fields R account6number ;balance.

A sample database appears in figure 0. $t shows that customer

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Only one-to-many and one-to-one relationships can be directlyrepresented in the hierarchical model. If the relationship is many tomany, then two separate tree-structure diagrams, T1 and T2, each ofwhich has the customer and account record types, should be created.In tree T1, customer acts as the parent record; in tree T2, account actsas parent record.

25 6et4or* Model-

&he networ% data model is a variant of the hierarchical data model. /atabases can betranslated from hierarchical to networ% and vice versa in order to optimize processingspeed and convenience. i%e a hierarchical database, networ% database consists of acollection of records connected to one another through lin%s. 3ach record is a collection

of fields Jattributes*, each of which contains only one data value.Cetwor% model depicts many6to6many relationships. $n other words, parents can havemultiple children and a child can have more than one parent.

As an illustration, we consider a database representing a customer6account relationship ina ban%ing system. &here are two record types( customer and account. &he customerrecord type consists of three fields( customer6name, customer6street, and customer6city.imilarly, the account record consists of two fields( account6number and balance.

Figure 1 shows therelationship is many tomany from customer toaccount, a customer canhave more than oneaccount, as does ohnson,mith both have twoaccounts. And the accountA6+@) belongs to bothohnson and smith

Figure 1

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$f the relationship is many to many, for e'ample if ohnson has accounts A6)@) and A6+@) and that account A6+@) is owned by both ohnson and mith. &hen the sample

database will be similar to the following figure.

3) Relational Model (RDBMS or Relational Database Management

System)

A relational Model consists of collection of tables each of which assigned a uniue name.A table is two6dimensional structure called relations that are the logical euivalent offiles. Actually ?/#M stores data in the form of related tables.A row in a table represents a relationship among a set of values and a table is a collectionof such relationship. &he term Ttuple is used to represent a row. All rows of a table aredistinct. $n other words, no two rows which are identical in every column.All tuples have same fields: the term Tattribute is used instead of Tfield in case of?elational model.8rdering of rows ; columns within a table is immaterial9onsider a database that represents a customer6account relationship in a ban%ing system.&here are three relations( customer, account ; account6owner represented by three tables.&he customer relation consists of three attributes( customer6name, customer6street, andcustomer6city. &he account relation consists of two attributes( account6number andbalance. Account6owner consist of two attributes customer6name, account6number

0able - %ustomer

A sample database is shownin figure 2. &he figureshows

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%ustomer-name %ustomer-street %ustomer-city

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table that is sufficiently normalized is not vulnerable to problems of this %ind, as itsstructure prevents it from holding redundant information in the first place.A table that is not sufficiently normalized can suffer from logical inconsistencies ofvarious types, and from anomaly involving data operations.

)* '(date anomaly-&he same information can be e'pressed on multiple records:therefore updates to the table may result in logical inconsistencies.

+* ,nsertion anomaly 60here is circumstances in 4hich certain facts cannot berecorded at all.

5 #eletion anomaly- &here is circumstances in which the deletion of data representingcertain facts necessitates the deletion of data representing completely different facts.

For e'ample, each record in an "3mployees=%ills" table might contain an 3mployee $/,3mployee Address, and %ill: thus a change ofaddress for a particular employee willpotentially need to be applied to multiplerecords Jone for each of his s%ills*. $f theupdate is not carried through successfullyif,that is, the employee=s address is updated on

some records but not othersthen the table isleft in an inconsistent state. pecifically, thetable provides conflicting answers to theuestion of what this particular employee=saddress is. &his phenomenon is %nown as anupdate anomaly.

For e'ample, each record in a "Faculty and&heir 9ourses" table might contain aFaculty $/, Faculty Came, Faculty

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$deally, a relational database table should be designed in such a way as to e'clude the

possibility of update, insertion, and deletion anomalies. &he normal forms of relationaldatabase theory provide guidelines for deciding whether a particular design will bevulnerable to such anomalies. $t is possible to correct an un6normalized design so as toma%e it adhere to the demands of the normal forms( this is called normalization.

Cormalization typically involves decomposing an un6normalized table into two or moretables that, were they to be combined J!oined*, would convey e'actly the sameinformation as the original table.

16F 6A relation is in first normal form J)CF* if and only if the domain of an attribute

must include only atomic Jsimple, indivisible* values and that the value of any

attribute in a tuple must be a single value from the domain of that attribute.

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location of a department. &his decomposes the non6)CF relation into two )CFrelations.

#/PA0M/601

/CAM3 /C>M#3? /ME?3C8?esearch 0 ---0000

Administration 54210-+)

M#3? X 7CAM3, 789A&$8C

&o ma%e the relation in +CF we brea% the above relation into three different relations,each of which in +CF3M7S7?8)

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3C8 7C>M#3? ?

3M7S7?8+

3C8 3CAM3

3M7S7?8-7C>M#3? 7CAM3 789A&$8C

6F-

A relation schema ? is in -CF if it satisfies +CF and no nonprime attribute of ? istransitively dependent on the primary %ey. $n other words relation should not have anon%ey attributes functionally determined by another non6%ey attribute Jor by a set ofnon%ey attributes*.

A functional dependency D X W in a relation schema ? is a transitive dependency if

there is a set of attributes Y that is neither a candidate %ey nor a subset of any %ey of ?,"and both DX Y and YXW hold.

Following table in +CF since no partial dependencies on a %ey e'ists. #ut not in -CF.

3M7S /37&

3CAM3 3C8 /8# A//?3 /C>M#3? /CAM3 /ME?3C8

&he dependency 3C8X/ME?3C8 is transitive through /C>M#3? in 3M7S/37&because both the dependencies 3C8X/C>M#3? and /C>M#3? X /ME?3C8hold and /C>M#3? is neither a %ey itself nor a subset of the %ey of 3M7S /37&.

$ntuitively, we can see that the dependency of /ME?3C8 on /C>M#3? is undesirablein 3M7S/37& since /C>M#3? is not a %ey of 3M7S/37&.&o ma%e the relation in -CF we brea% the above relation into two different relations, eachof which in -CF

3M7S /37&)

3CAM3 3C8 /8# A//?3 /C>M#3?

3M7S /37&+

/C>M#3? /CAM3 /ME?3C8

'sers of the database -&he database management system is responsible for controlling interaction between the

database and application software. &here are three distinct classes of users of the

database. &hey are(

). $nformation pecialist6 $nformation pecialists are responsible for the

designing of the database. &hey use database in application system that a re

being designed and developed.

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+. /atabase Administrator6 /atabase administrators use special features and

functions of the database management system to create, update and

maintain the database and ensure integritycontrols.

-. Actual >sers6 the actual users of the database ma%e use of the database for their

functional assignments through ueries.

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/xam(le 1 - A Iche;ue (rocessing systemJ in a ban*. All the cheue received in a

particular time frame, say, on a particular day, are grouped together to produce a batch oftransaction. &hey are then %eyed to tape and sorted into a transaction file by the accountnumber as indicated above. &his is then read in order by the &7 program. &he old masterfile, which is also sorted by the account number, contains customer chec%ing account datafrom the prior period. &7 program also reads the stored data, processes the transactions,and data is updated to create the new customer master file. $n this process, it generatesreports. &he outputs may be overdrawn accounts, monthly summaries, suspicious activityetc.

/xam(le 2hen the total processing involves e'ecution of several programs, batchprocessing underta%es each program in a seuence. For e'ample, in preparing an $nvoice,

&he steps involved are(). /ata entry of delivery documents+. Galidations of delivery documents data-. 9omputation of $nvoice. >pdating of delivery transaction file0. 7rinting of $nvoice1. >pdating $nvoice &ransaction File

$n batch processing, data about several delivery documents is accumulated and a batch oftransactions is created. &his batch of transactions is then processed in seuence. &hebatch processing produces all invoices in one go when the batch is over.

/ata entry

of

accumulated

documents

$nputJ#atched* 8utput

Architecture of a batch transaction (rocessing A((lication

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#atch processing has advantages and limitations.

)atch (rocessing has these adantages

$t shifts the time of !ob processing to when the computing resources are less busy. $t avoids idling the computing resources without minute6by6minute human

interaction and supervision.

#y %eeping high overall rate of utilization, it better amortizes the cost of a

computer, especially an e'pensive one.

)atch (rocessing is economical 4here

). &ransaction volumes are very large+. /edicated hardware is not available-. $mmediate uery replies are not needed. $nstant updates are not essential

)atch (rocessing has limitation such as

orted seuential files are used. &ime spent on sorting the data as per reuirement.

8utputs are available only in batches. $mmediate outputs are not available.

File updating is done at the end of processing cycle. $mmediate enuiry will

produce wrong results.

/xam(les of useAn electricity company produces its monthly bills for customers. All the meter readingwould be collected in or estimated over the month then the data batch processed and thebills calculated and printed out.

:uic* es(onse !ystems

Buic% response systems are designed to provide response on time and effectively. uchsystems allow users to react more rapidly to changing conditions. Buic% responsesystems can be categorized in four ma!or groups. &hey are( 8n6line systems

8n6line real time systems

&ime sharing

/istributed processing

On-line systems

&his concept of on6line processing is in contrast with batch processing. &ransactions areinput into the system as soon as they arise. &hey are used to process a single transactionat a time. $t allows immediate computations and updating of files. 8nline transactionprocessing involves a direct connection between the operator and the &7 program.

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the processing ta%es place, as the data is input but the system does not need to be instant,a delay of a few seconds is not critical. &he limitations of batch processing had restrictedapplications of computers in certain fields. 8n6line systems have opened up a vastapplication area for computers. &he concept of on6line applied to commercialapplications resulted in a methodology termed as "on6line transaction processing" or

8&7. 8&7 has also been used to refer to processing in which the system respondsimmediately to user reuests.

On-line systems re;uirements

8n6line system reuires some specific features in the hardware and software. &hehardware features reuired by on6line systems include increased memory, higher speedand increased secondary storage. &he software features reuired by on6line systemincludes special record handling features, record loc%ing and archiving for crashrecovery.

&oday=s online transaction processing increasingly reuires support for transactions thatspan a networ% and may include more than one company. For this reason, new 8&7software uses clientPserver processing that allows transactions to run on differentcomputer in a networ%.

/xam(leaving ban% accounting system

On-line eal 0ime !ystems

&he term real time means occurring immediately. ?eal time processing means that, notonly is input data processed immediately, but output results are available fast enough to

meet the immediate information needs of end users.?eal6time processing is generally used in environments where a large number of events,mostly e'ternal to the computer system, must be accepted and processed in a short timeor within certain deadlines. A primary ob!ective of real6time systems is to provide uic%event6response times. Applications embedded in telephone switching euipment, flightcontrol, robot etc.

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communication networ% Jusually by ocal Area Cetwor%*, such that a single dataprocessing tas%s can span through several machines in the networ%. &he networ%management software handles the communication between the machines. Mostdistributed processing systems contain sophisticated software that detects idle 97>s onthe networ% and parcels out programs to utilize them. Another form of distributed

processing involves distributed databases, in which the data is stored across two or morecomputer systems. &he database system %eeps trac% of where the data is so that thedistributed nature of the database is not apparent to users. A single application should beable to operate transparently on data i.e., spread across a variety of different databases,managed by different /#M, running on variety of different communication networ%.

#ifferentiate bet4een batch mode and online mode (rocessing

)atch mode (rocessing Online mode (rocessing

#atch processing is a large scale of

processing which is done in batches andinputs are also entered in batches by%eyboard and stored in transaction files

8nline processing means users directly

enter information online Jusually, online, inthis case, means online to a centralprocessor, rather than its modernconnotation of the $nternet, but it couldmean both*

Pmemory bound not

$P8 bound. ince no $P8, no 97> timewaste and as a result it is very fast process.

&he online mode processes are mainly $P8bound. &ime wasted to perform $P8 as aresult it is relatively slow than batch

processing.

ince it is done without human interactionit can be shifted the when the computingresources are less busy. $t can be shifted inless busy business hour or it can be run inovernight.

ince it is interactive, this can only be donein office hour.

#atch processing can process huge amounts $t is not suited for huge amount of data

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of data processing.

#atch processing is very cheap to run.

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less busy business hour or it can be run inovernight.

#atch processing can process huge amountsof data

$t is not suited for huge amount of dataprocessing.

#atch processing is very cheap to run.

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%haracteristics of %lient + !erer

%haracteristics of a client

$nitiates reuests aits for and receives replies

>sually connects to a small number of servers at one time

&ypically interacts directly with end6users using a graphical user interface

%haracteristics of a serer

7assive Jslave*

aits for reuests from clients

>pon receipt of reuests, processes them and then send replies

>sually accepts connections from a large number of clients &ypically does not interact directly with end6users

&he whole point of client6server architecture is to distribute components of an applicationbetween a client and a server so that, for e'ample, a database can reside on a servermachine Jfor e'ample mainframe* and its management is done by /#M, a user interfacecan reside on a client machine Ja des%top 79*, and the business logic can reside in eitheror both components. &he client handles server independent tas%s through its storedapplication logic and server handles clients reuest, which are triggered after processingin the client.

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would allow the user to register a new transaction that will then be sent to the serverfor storing in the database.

04o-tier %lient !erer Architecture E#iagram and #escri(tion5

&wo tier architectures consist of three components distributed in two layers( clientJreuester of services* and server Jprovider of services*. &he three components are

>ser ystem $nterface7rocessing Management Jor #usiness rules*/atabase Management

&he two6tier design allocates the user system interface e'clusively to the client. $t placesdatabase management on the server and splits the processing management Ji.e., programs

to implement #usiness rules*between client and server, creating two layers.

0hic* and 0hin %lient

A fat client or thic% client is a computer Jclient* in clientRserver architecture whichtypically provides rich functionality independent of the central server. $t still reuires atleast periodic connection to a central server, but is often characterized by the ability toperform many functions without that connection.

A thin client Jsometimes also called a lean or slim client* is a computer which dependsheavily on some other computer Jits server* to fulfill its traditional computational roles. Athin client generally does as little processing as possible and relies on accessing the servereach time input data needs to be processed.

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$n many two6tier designs, most of the application portion of processing is in the clientenvironment. &he database management server usually provides the portion of theprocessing related to accessing data Joften implemented in store procedures*. 9lientscommonly communicate with the server through B statements. $t should be noted thatconnectivity between tiers could be dynamically changed depending upon the user=sreuest for data and services.>sage 6 &wo tier software architectures are used e'tensively in non6time criticalinformation processing where management and operations of the system are not comple'.&his design is used freuently in decision support systems where the transaction load islight. &wo tier software architectures reuire minimal operator intervention. &he two tierarchitecture wor%s well in relatively homogeneous environments with processing rulesJbusiness rules* that donot change very often and when wor%group size is e'pected to be fewerthan )@@ users, such as in small businesses.

imitation of &wo6&ier 9lient erver Architecture6

!calability-&he two6tier design will scale6up to service )@@ clients on a networ%. $tappears that beyond this number of users, the performance deteriorates. &his is becausethe client and server e'change "%eep alive" messages continuously, even when no wor% isbeing done, thereby saturating the networ%.estricts flexibility and choice of #)M! -$mplementation of processing managementservices using vendor proprietary database procedures restricts fle'ibility and choice of/#M for applications.!ystem administration and configuration- &wo tier architectures can be difficult to

administer and maintain because when applications reside on the client, every upgrademust be delivered, installed, and tested on each client. &he typical lac% of uniformity inthe client configurations and lac% of control over subseuent configuration changesincrease administrative wor%load.

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0hree-tier %lient !erer Architecture -

&he three6tier software architecture overcomes the limitations of the two6tier. &he threetiers of three6tier software architecture are as follows(

7resentation tier Jthe client or front6end*,

Application tier Jthe application server, or middleware* ;

/atabase tier J/ata erver*

&he application tier Jmiddle tier server* is between the presentation tier Jclient* anddatabase tier. &he three6tier design allocates the user system interface e'clusively to thepresentation tier. $t places database management e'clusively on the data server. &his

middle tier provides process management where business logic and rules are e'ecutedand can accommodate hundreds of users Jas compared to only )@@ users with the two tierarchitecture* by providing specialized functions.

A three tier distributed clientPserver architecture includes a user system interface

top tier where user services Jsuch as session, te't input, dialog, and displaymanagement* reside.

&he middle tier servers are typically coded in a highly6portable, non6proprietary

language such as 9.

&he third tier provides database management functionality can be implemented

without using any proprietary database management system languages. &he datamanagement component ensures that the data is consistent throughout thedistributed environment through the use of features such as data loc%ing,consistency, and replication.

$t should be noted that connectivity between tiers could be dynamically changeddepending upon the user=s reuest for data and services.

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&he middle tier server Jalso referred to as the application server* improves performance,fle'ibility, maintainability, reusability, and scalability by centralizing process logic.9entralized process logic ma%es administration and change management easier bylocalizing system functionality so that changes must only be written once and placed onthe middle tier server to be available throughout the systems.

'sage -&hree tier architectures are used in commercial and military distributedclientPserver environments.

6-tier architecture

An C6tier architecture Jwith C more than -* is really - tier architectures in which themiddle tier is split up into new tiers. &he application tier is bro%en down into separateparts. hat these parts are differs from system to system. &he following picture shows it(

#istributed #atabase

$n recent years, distributed databases have become an important area of informationprocessing, and it is easy to foresee that their, importance will rapidly grow. &here areboth organizational and technological reasons for this trend( distributed databaseseliminate many of the shortcomings of centralized databases and fit more naturally in thedecentralized structures of many organizations.

&wo eually important aspects of a distributed database(

#istribution7i.e., the fact that the data are not resident at the same site Jprocessor*, so

that we can distinguish a distributed database from a single, centralized database.

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applications. 3ach site also participates in the e'ecution of at least one globalapplication, which reuires accessing data at several sites using a communicationsubsystem.

/xam(les

9onsider a ban% that has three branches at different locations. At each branch a computer

controls the teller terminals of the branch and the account database of that branch. 3achcomputer with its local account database at one branch constitutes one site of thedistributed database: a communication networ% connects computers.

/uring normal operations the applications, which are reuested from the terminals of abranch, need only to access the database of that branch. &hese applications arecompletely e'ecuted by the computer of the branch where they are issued, and willtherefore be called local applications. An e'ample of a local application is a debit or acredit application performed on an account stored at the same branch at which theapplication is reuested.

$f we try to apply the definition of distributed databases to the situation described so far,we find that it is difficult to say whether the logical correlation property holds. From atechnological viewpoint, it appears that the important aspect is the e'istence of someapplications, which accesses data at more than one branch. &hese applications are calledglobal applications or distributed applications. &he e'istence of global applications willbe considered the discriminating characteristic of distributed databases with respect to aset of local databases.

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A typical global application is a transfer of funds from an account of one branch to anaccount of another branch. &his application reuires updating the databases differentbranches. Cote that this application is something more than !ust performing two localupdates at two individual branches Ja debit and a credit*, because it is also necessary toensure that either both updates are performed or neither.

hy distributed databases architecture better oer multi user center database

architecture3

&here are several reasons why distributed databases architecture better over multi usercenter database architecture. &he following is a list of the main motivations.

). 8rganizational and economic reasons6 Many organizations are decentralized, anda distributed database approach fits more naturally the structure of theorganization. ith the recent developments in computer technology, theeconomy6of6scale motivation for having large, centralized computer centers isbecoming uestionable. &he organizational and economic motivations areprobably the most important reason for developing distributed databases.

+. $nterconnection of e'isting databases6/istributed databases is the natural solutionwhen several databases already e'ist in an organization and the necessity ofperforming global applications arises. $n this case, the distributed database iscreated bottom6up from the pree'isting local databases. &his process may reuirea certain degree of local restructuring: however, the effort, which is reuired bythis restructuring, is much less than that needed for the creation of a completelynew centralized database.

-. $ncremental growth6$f an organization grows by adding new, relativelyautonomous organizational units Jnew branches, new warehouses, etc.*, then thedistributed database approach supports a smooth incremental growth with aminimum degree of impact on the already e'isting units. ith a centralizedapproach, either the initial dimensions of the system ta%e care of future e'pansionwhich is difficult to foresee and e'pansive to implement, or the growth has ama!or impact not only on the new applications but also on the e'isting ones.

. ?educed communication overhead6 $n a geographically distributed database thefact that many applications are local clearly reduces the communication overhead

with respect to a centralized database. &herefore, the ma'imization of the localityof applications is one of the primary ob!ectives in distributed database design.

0. 7erformance considerations &he e'istence of several autonomous processorsresults in the increase of performance through a high degree of parallelism.

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1. ?eliability and availability6 &he distributed database approach, especially withredundant data, can be used also in order to obtain higher reliability andavailability. &he autonomous processing capability of the different sites does notby itself guarantee a higher overall reliability of the system, but it ensures a faulttolerance property( in other words, failures in a distributed database can be more

freuent than in a centralized one because of the greater number of components,but the effect of each failure is confined to those applications which use the dataof the failed site, and complete system crash is rare.

Features of #istributed ersus %entralized #atabases/istributed databases processing has different features from traditional, centralizedsystems. $t is therefore useful to loo% at the typical features of traditional centralizeddatabases and to compare them with the corresponding features of distributed databases.

Features %entralized #atabase Processing #istributed #atabase Processing

9entralizedcontrol

/atabase administrator has centralcontrol over the database. &hefunction of /#A include(

chema definition

torage structure ; access

method definition

chema and physical6

organization modification.

Eranting authorization of

data access.

?outine maintenance

$n distributed databases, the idea of

centralized control is much less emphasized.$n general, in distributed databases it is

possible to identify a hierarchical control

structure based on a global database

administrator, who has the central

responsibility of the whole database, and on

local database administrators, who have the

responsibility of their respective local

databases.

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two reasons( first, inconsistenciesamong several copies of the samelogical data may arise and thereuirement of storage space isincreased if the data are redundant.

redundancy as a desirable feature( first, thelocality of applications can be increased ifthe data is replicated at all sites whereapplications need it, and second, theavailability of the system can be increased,

because a site failure does not stop thee'ecution of applications at other sites if thedata is replicated. $n general, the samereasons against redundancy, which weregiven for the traditional environment, arestill valid and therefore the evaluation of theoptimal degree of redundancy is reuired.As a very general statement, let us say thatthe convenience of replicating a data itemincreases with the ratio of retrieval accessversus update accesses performed by

applications to it. &he convenience of datareplication increases because if we haveseveral copies of item retrieval can beperformed on any copy, while updates mustbe performed consistently on all copies.

7rivacy andsecurity

$n traditional databases, the databaseadministrator, having centralizedcontrol, can ensure that onlyauthorized access to the data isperformed. 9entralized databaseapproach in itself, without

specialized control procedures, ismore vulnerable to privacy andsecurity violations

&wo peculiar aspects of distributeddatabases are worth mentioning( first, in adistributed database with a very high degreeof site autonomy, the owners of local datafeel more protected because they canenforce their own protections instead of

depending on a central databaseadministrator: second, security problems areintrinsic to distributed systems in general,because communication networ%s canrepresent a wea% point with respect toprotection.

#iscuss the meritsKdemerits of non-re(licated7 (artial re(licated and fullyre(licated database.

Merits of non -re(licated database

)* ess storage space reuirement

+* $ncrease the performance of update access since because single copy of anydata need to be updated.

-* &he chance of inconsistency among several pieces of same data eliminated.#emerits of non -re(licated database

)* Availability of the system reduced because in absence of redundant data adatabase crash cause stop e'ecution.

+* $f any data accidentally deleted, there is no way to get bac% it.-* /ecease the performance of retrieval access.

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Merits of (artial -re(licated database

)* More storage space reuirement than non6replicated database but less spacereuirement than fully replicated database.

+* $f one copy of data accidentally deleted, it can be recovered if it was replicated

-* Availability of the system increased because of replication* $ncrease of performance for retrieval access than non6replicated database#emerits of (artial -re(licated database

)* /ecrease the performance of update access cause more than single copy ofany data needs to be updated. #ut its performance is more than fullyreplicated database in case of update access.

+* &here is chance of inconsistency among several pieces of same data.

Merits of fully -re(licated database

)* $ncrease of performance for retrieval access than non6replicated ; partialreplicated database because among several copies of item retrieval can be

performed on any copy+* Availability of the system increased because of replication-* $f one copy of data accidentally deleted, it can be recovered

#emerits of fully -re(licated database)* More storage space reuirement than non6replicated and partially replicated

database+* /ecrease the performance of update access cause more than single copy of

any data needs to be updated.-* &here is chance of inconsistency among several pieces of same data.

hat are the (ro(erties of #istributed #ata Processing3 /x(lain each of them

/istributed processing has following properties(

15

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25 6o reliance on a centralized site - &here must not be any reliance on a centralmaster site for some central service, so that the entire system would dependent onthe central site. ?eliance of central site is undesirable for the reason that thesystem would be vulnerable. A single failure can totally sto( total(rocessing in case of centralized (rocessing because single (rocessor

and non-redundant data is used. ,n distributed (rocessing a((roach7es(ecially redundant data and existence of more (rocessor can beused to obtain higher reliability and aailability. 0he effect of each

failure is confined to those a((lications7 4hich use the data of the

failed site7 and com(lete system crash is rare.

5 %ontinuous O(eration6 &here should ideally never be any need for a plannedentire system shutdown. $ncorporating a new site into an e'isting distributedsystem or removing an e'isting site from distributed system should not cause anyunnecessary interruptions in service.

"5 sers are not reuired to %now the physical location ofthe data in the distributed processing system: they should be able to find any dataas long as the data identifiers are supplied.

$5 e(lication ,nde(endence->sers view each data ob!ect as logically uniue. &hedistributed system may replicate an ob!ect to increase either system performanceor data availability. >sers do not have to be concerned with what data ob!ectshave been replicated or where replicas have been placed.

&5 Fragmentation ,nde(endence-&he system partitions the relations into severalfragments, and stores each fragment at a different site. >sers are not reuired to%now how a relation has been fragmented.

B5 #istributed :uery Processing-$t is crucially important for a distributedenvironment to choose a good strategy for distributed uery processing sinceuery processing in a distributed system reuire some amount of datacommunication among sites along with local 97> and $P8 activity.

C5 #istributed 0ransaction Management- &wo ma!or aspects of transactionmanagement is recovery control and concurrency control reuired e'tended

treatment in distributed environment since in a distributed system a singletransaction can involve the e'ecution of codes at multiple sites and can thusinvolve updates at multiple sites.

D5 ard4are ,nde(endence-

1L5 O(erating !ystem ,nde(endence-

115 6et4or* ,nde(endence-

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>sers should be presented with the Tsingle system image regardless any particularhardware platform, operating system and Cetwor%.

125 #)M! ,nde(endence- $deal distributed system should provide /#Mindependence.

#ata %ommunications and 6et4or*s

#efinition of #ata communications6/ata communication is the e'change of databetween two devices via some from of transmission medium such as a wire cable. For adata communication to occur, the communicating devices must be a part ofcommunication system made up of a combination of hardware Jphysical euipment* andsoftware Jprogram*. &he effectiveness of a data communication system depends on threefundamental characteristics( delivery, accuracy, and timeliness.

). #eliery6 &he system must deliver data to the correct destination. /ata must bereceived by the intended device or user and only by that device or user.

+. Accuracy6 &he system must deliver the data accurately. /ata that have beenaltered in transmission and left uncorrected are unusable.

-. 0imeliness6 &he system must deliver data in a timely manner. /ata delivered lateare useless. $n the case of video and audio, timely delivery means delivering dataas they are produced, in the same order that they are produced, and withoutsignificant delay. &his %ind of delivery is called real6time transmission.

%om(onents of data communications system- A data communication system hasfive components.

). Message-&he message is the information Jdata* to be communicated. $t canconsist of te't, numbers, pictures, sound, or video6or any combination of these.

+. !ender-&he sender is the device that sends the data message. $t can be acomputer, wor%station, telephone handset, video camera, and so on.

-. eceier-&he receiver is the device that receives the message. $t can be acomputer, wor%station, telephone handset, television, and so on.

. Medium6&he transmission medium is the physical path by which a messagetravels from sender to receiver.

0. Protocol- A protocol is a set of rules that governs data communications. $trepresents an agreement between the communicating devices. ithout a protocol,two devices may be connected but not communicating, !ust as a person spea%ing

French cannot be understood by a person who spea%s only apanese.

H0y(es of 0ransmissions Media

&ransmission media can be divided into two broad categories( guided and unguided.

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Euided media are those that provide a physical conduit from one device to another. Asignal traveling along any of this media is directed and contained by physical limits of themedium. 3'amples are(

&wisted pair cable

9oa'ial cable

Fiber6optic 9able

04isted (air cable6A type of cable that consists of two independ

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