Chapter 1 Database Systems

8/12/2019 Chapter 1 Database Systems

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BACS 485 -- Chapter 1

Chapter 1: Database Systems

See document: Lecture_Material.mmap

I. Objectives The difference et!een data and information "hat a data a#e i#$ t%pe# of data a#e#$ !h% u#eful in u#ine## "h% i# data a#e de#i&n important'

(o! did the data a#e approach e)ol)e from file #%#tem#' The characteri#tic# of file mana&ement #%#tem# The characteri#tic# of data a#e mana&ement #%#tem# (o! *BMS and a data a#e are different.

II. Data vs. Information

A. Data+a! fact# a out a per#on$ place$ or thin& ,#imilar to a noun . The e% characteri#tic i# that it i#

not particularl% u#a le in it# pre#ent form % the end-u#er.

B. Information*ata that ha# een proce##ed ,or manipulated into a form that i# more u#a le % the end u#er.A e% characteri#tic i# that one per#on# data can e another per#on# information. /t# all amatter of per#pecti)e.

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Ta en to the ne2t le)el$ information that i# a out a #pecific topic and can e applied to #ol)e pro lem# can e called no!led&e.

III. Database & DBMS

A. DBMS *ata a#e mana&ement #%#tem. A collection of pro&ram# u#ed to mana&e the data a#e #tructure,i.e.$ metadata and the data it#elf ,data a#e . ro)ide# #tructure and control needed to acce##and #ecure the data a#e.

B. DatabaseThe actual data that i# #tored % the or&ani3ation. /t i# or&ani3ed and #tructured in #uch a !a%to maintain inte&rit% and #ecurit%. Acce##ed onl% throu&h the *BMS.

C. Metadata

The #tructural component of the *BMS. A de#cription of the data characteri#tic# and therelation#hip# et!een the data item#. Similar to the #tructure u#ed to or&ani3e a li rar%.

D. Types of DatabasesThere are different !a%# to refer to data a#e# ,and *BMS# . Some are a#ed on &eo&raphic location of the datait#elf$ other# are a#ed on the num er of concurrent u#er#$ #till other# are related to the hard!are that the *BMSrun# on. Belo! are #ome of the common t%pe#.

Single-user database - #upport# onl% a #in&le u#er at a time. #uall% onl% !or # on a C

Multi-user database - #upport# #e)eral u#er# at the #ame time. Can e C or mainframe a#ed.

Desktop database - #in&le u#er data a#e that run# on a C al#o called de# top data a#e

Workgroup database - Small multi-u#er data a#e ,u#uall% 56 u#er# or le##

Enterprise database - Lar&e multi-u#er data a#e. #uall% run# on a mainframe.

Centralized database - *ata a#e that #upport# data in a #in&le ph%#ical location.

Distributed database - *ata a#e that #upport# data acro## #e)eral &eo&raphical location# ,re7uire# a net!or

IV. Why DB esi!n important"

A. Redundancy Situation that occur# !hen the #ame piece of information i# #tored multiple time# in adata a#e. /# con#idered ad ecau#e it cau#e# a ho#t of other pro lem#. or e2ample$ if acu#tomer# addre## i# #tored #e)eral time# in the data a#e$ an update mi&ht onl% affect one ort!o of the copie#. /n the future$ mailin !ould #ometime# &o to the proper addre##$ othertime# it !ould not. Thi# cau#e# poor data inte&rit% and ma e# the cu#tomer not tru#t theinformation produced % the #%#tem.

/t i# impo##i le to &et rid of all data redundanc%. Some i# needed to lin the )ariou# piece# ofdata to&ether. (o!e)er$ unnece##ar% redundanc% i# a #i&n of poor data a#e de#i&n and #hould

e a)oided. 9ou #tri)e to achie)e controlled redundanc%.

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B. Integrity *ata !ith &ood inte&rit% i# #aid to e:

1. Accurate - matche# the real !orld ,i.e.$ it i# ri&ht

. Complete - not mi##in& an% e% information

;. Timely - i# a)aila le !hen %ou need it

4. Reliability - the #ame an#!er i# pro)ided if nothin& chan&e# and the #ame 7ue#tion i# a# eda&ain

C. Agility ne of the re#ult# of the#e manual #%#tem# !a# that each functional area o!nedtheir data and ecame )er% po##e##i)e of it. Thi# !a# >? for then.

"hen computer# !ere introduced it &a)e a !a% to automate manual ta# #. ,/n fact$the title computer u#ed to appl% to a per#on that did manual computation#.

Allo!# compan% to:

- #peed up ta# # ,!ithout infinite per#onnel - &et etter ta# inte&rit% ,accurac% - &ro! companie# i&&er

Thi# !a# a i& deal. Much fan- fare. eople e2pected lot#. The i& companie#!ere the fir#t to u% computer#.

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The earl% computer# !ere )er% e2pen#i)e and not )er% u#er- friendl%. The% co#t #omuch that the% !ere applied to the area# !here the chance of #ucce## !a# e#t ,i.e.$

pa%- ac of the hu&e in)e#tment .

The e#t area to &et 7uic pa%- ac ,and &et lot# of &ood + !a# to automate

independent application #%#tem# to automate @o # of clerical !or er# and #ol)e a#pecific pro lem. or e2ample$ pa%roll$ account# pa%a le$ purcha#in&$...

Thi# &a)e earl% computer #%#tem# a ad reputation for puttin& people out of !or,the% #till ha)e that reputation to #ome people .

The earl% #%#tem de#i&ner# tried to pro&ram the computer e2actl% the #ame a# themanual #%#tem. Thi# !a# ea#ier$ ut tended to prolon& the fiction of functional datao!ner#hip.

The #%#tem and it# data !ere o!ned % the department re#pon#i le for thefunction. The data !a# con#idered a pri)ate re#ource.

Computer technolo&% ad)anced and #%#tem# &re! more po!erful$ ut thefunctional u#er# #till con#idered data to e a pri)ate re#ource. ,A fiefdom . Thi#!a# BA*

Al#o$ each time a ne! application !a# de)eloped$ ne! file# !ere defined. /t too%ear# for people to reali3e ,and reall% #tart to do #omethin& a out treatin& data a# acorporate re#ource that need# to e mana&ed. Thi# !a# one of the factor# that#tarted the data a#e mo)ement.

/ma&ine #ituation !here mone% i# not mana&ed in compan%. ach department ha#

a pile the% control. o #harin&$ no cro##- department information #harin& a out themone%. /f i& purcha#e came up$ no !a% to con#olidate mone% to ma e it. /t i#ridiculou# to con#ider$ ut that i# e2actl% the #ituation of the traditional approach.

A. Traditional Approach/n the traditional approach$ computer #%#tem# are de#i&ned for and u#ed %indi)idual department# for #pecific ta# #. ach department maintain# and o!n#their o!n data. Thu#$ little #harin& ta e# place et!een department# ,onl% that#harin& that i# mandated and re7uired .

ach ne! #%#tem u#uall% uild# it# o!n data file# rather than tr% to acce##e2i#tin& one# ecau#e to tou&h to coordinate modification# and re7uirement#.

A central * #hop pro)ide# the pro&rammin& #er)ice for the functionaldepartment# , ut it i# #till the department=# data . The * #hop mu#t #omeho!mana&e all pro&rammin& need# for the !hole compan% !ithout the enefit of a&lo al plan or centrali3ed authorit%. Der% tou&h to do

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Lar&e ac lo characteri3ed thi# #etup. /mpatient department# #ometime# uilttheir o!n mini-* #hop to handle their o!n pro&rammin& need#$ ut that #eldom!or ed ecau#e e2i#tin& data #harin& &oe# a!a%.

B. Database ApproachThe data a#e approach doe# a!a% !ith the m% data #%ndrome. /t collect# alldata into an or&ani3ed repo#itor%.

The approach rin a ne! !a% of thin in& and #ome ne! tool# that permit thecontrol of redundanc%$ impro)ed fle2i ilit%$ and centrali3ed data control.

; feature# characteri3e the data a#e approach:

1. Share-ability o data . Centralized data management and control ;. Adaptability

(ere=# a #ummar% of the approach...

The data a#e approach e&in# % uildin& a model of the or&ani3ation ,called anenterpri#e model . The model #ummari3e# the #tructure of the data u#ed ,andneeded in the compan%. /t #ho!# the data entitie# and the relation#hip# et!eenthem.

,/n real life$ %ou #eldom ha)e a &lo al enterpri#e model$ rather %ou ha)e acollection of #maller #%#tem model#. Their collected !hole i# e7ui)alent to theenterpri#e model idea.

The #tructure i# carefull% uilt #o that all u#er# need# are ta en care of !ith aminimum of redundanc%. ,Thu#$ #harin& and redundanc% are oth #ol)ed.

e2t$ %ou de#cri e thi# #tructure to a piece of #oft!are ,called a *BMS that canmaintain oth it and data in it# format. inall% %ou load the data and u#e the*BMS to acce## and maintain the it and it# #tructure.

/t i# the role of the *BMS to retrie)e and #tore the data. Al#o the *BMS doe# it# e#t to ma e #ure the data are accurate ,not nece##aril% correct .

VI. ra itiona$ Systems 'ros & Cons

A. Pros

1. Simp$eThe traditional file proce##in& method !a# the ea#ie#t !a% for #%#tem# tode)elop &i)en the current #tate-of-the-art. Tho#e people in the 56=# !eren=t#tupid. The% reali3ed that the #ituation !a# not ideal$ it=# @u#t that the computer



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technolo&% !a# limited ,e.&.$ tape# and card# !ere a)aila le$ not di# # . ,Later$it #ta%ed popular ecau#e of momentum and the e2pen#e to chan&e. Al#o$ the#%#tem# that !ere automated !ere not the real mone%-ma er# for the compan%.Mar etin& and production ma e mone%. a%roll and nce a computeri3edmanual #%#tem !a# !or in&$ it !a# cheaper to lea)e it alone than to #e)erel%modif% it. ,The% did not no! %et that 86E of all pro&rammin& i#maintenance.

B. Cons

1. Distrib%te O+nership

/n traditional #%#tem# each functional department o!ned it# o!n data. Thi# i#the m% data #%ndrome. The% feel it i# their per#onal propert% ,li e officefurniture to do !ith a# the% plea#e. >ften the% are he#itant to let an%one el#e inthe compan% #ee it , ecau#e then their po!er !ould e dimini#hed Mer&in&data ecame a political proce##. *oe# not help &lo al competiti)ene##.

a! "ncontrolled Redundancyach ne! #%#tem re7uired ne! file# to e uilt ,#ince no one !ould #haree2i#tin& data e)en if technolo&% e2i#ted to ma e it po##i le . Lot# of data !a##tored multiple time#. >nce for each #%#tem that needed acce## to it. Thi#!a# ad ecau#e:

di# #pace i# !a#ted data mu#t e input #e)eral time# data mu#t e updated #e)eral time# ,multiple occurrence#

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data !a# incon#i#tent ,ne2t #ection

)er%one reali3ed that redundanc% !a# a pro lem$ ut not one ne! ho! tofi2 it #hort of &i)in& up control of their data .

b! #nconsistent dataThi# i# the !or#t of the pro lem# -- it re7uire# #pecial attention. "hen %ou#tore data #e)eral time# ,#e)eral place# %ou "/LL ha)e incon#i#tencie# notmatter ho! careful %ou are. The !or#t ca#e i# !here %ou mi## an update.Thu#$ %ou ha)e t!o ,or more )er#ion# of data... !hich i# correct' A more#u tle incon#i#tenc% i# !hen the update i# #li&htl% incorrect ,mi##pellin& ofname or different a re)iation or the timin& of the update i# incorrect ,rai#eafter G+ period... . Since each cop% of data i# o!ned % a different &roup$it i# reall% no one# re#pon#i ilit% to ma e #ure that it i# &lo all% correct.+e#pon#i ilit% fall# et!een the crac #. Thi# allo!# multiple )er#ion# of thetruth to e #tored in the computer. Thi# undermine# the u#er# confidence in adata a#e if it appear# to &i)e incorrect an#!er#. /t can al#o can me## upcu#tomer relation# if %ou #end &ood# to the !ron& addre## or ill for anincorrect in)oice.

c! #slands o in ormationA pro lem that redundanc% and the m% data #%ndrome cau#e# i# that &roup#de)elop their o!n data en)ironment# that are independentl% maintained.

The#e u#er# ecome #elf-#ufficient and cut off from other#. The% are not!illin& to #hare or recei)e information. ot onl% redundant data$ utredundant tool# and effort too.

(. ,imite Data Sharin!Since e)er%one ha# their o!n cop% of the data$ no one #hare#. Thi# !a#te# di##pace and perpetuate# the c%cle of independent file #%#tem#. or e2ample$ %ouare de#i&nin& a ne! #%#tem that could u#e data alread% defined and maintained

% other department#. Since the% are un!illin& to #hare ,and it !ould re7uire#ome re!rite of their ,!or in& #%#tem %ou decide to ta e the ea#% !a% outand @u#t re-enter the data. Thi# i# politicall% ea#ier and #impler for the moment$

ut i# )er% #hort #i&hted. /t dela%# fi2in& the pro lem.

-. Inf$e ibi$ity/ndependent i#land# of information do not ea#il% cooperate. "hen chan&e# areneeded it ecome# a political ni&htmare. eople ha)e to call in fa)or# and ma edeal# to &et thin done. /f 7uic action and re#pon#i)ene## are re7uired --

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for&et it. Thi# i# !here traditional file #%#tem# reall% #tart to hurt companie#. /tcau#e# lo## of u#ine## to more efficient competition. /n addition$ chan&e# tofile #tructure# cau#e a ripple effect in all the pro&ram# that acce## that data. ore2ample I-di&it 3ip code# !ere a i& headache. The %ear 666 pro lem !a# a

i&&er one. /ndependent file- a#ed #%#tem# tend to e de#i&ned for a #pecific purpo#e. The% do not ea#il% allo! un-planned proce##in&.

a! $o data independenceThi# i# )er% important. "hen data definition or proce##in& chan&e# in atraditional file #%#tem it re7uire# man% modification#. The rea#on for thi# i##imilar to the data redundanc% di#cu##ion a o)e. /n thi# ca#e$ the datadefinition i# redundantl% #tored. /n addition$ the !a% the data are proce##ed i#al#o #tored redundantl%. So$ %ou ha)e to ma e chan&e# in man% place# toaccommodate a #imple data chan&e. "hen %ou can ma e data

modification# !ithout chan&in& pro&ram# %ou ha)e data independence .

b! Ad %oc &ueries constrainedAnother re#ult of infle2i ilit% i# that it i# difficult to &et information in an%format other than the #tandard format. or in#tance$ #a% a mana&er a# # ,ofthe top of her head ho! man% red !id&et# !ere #old on the ea#t co#t to

people under 1 %ear# old' . Chance# are that a #pecial report doe# not e2i#t!ith thi# information. ,Called ad hoc 7uer% -- one time onl% 7uer% . To &etthe information a #pecial report mu#t e &enerated. ro&rammer time i#u#uall% ac lo&&ed for month# #o it i# ea#ier to pull the information % handfrom old report#. Thi# defeat# the purpo#e of the computer.

The data i# out there and !ould e fairl% ea#% to collect if proper tool#e2i#ted. Tool# ha)e een uilt to help fi2 thi# pro lem ,called 4th &enerationlan&ua&e# . The#e ma e it ea#ier for non- pro&rammer# to do ad hoc 7uerie#$

ut #till re7uire# in-depth no!led&e a out !here and ho! the data are#tored. Mo#t mana&er# don=t no! ,or care to no! thi#.

/. 'oor stan ar s enforcement

Another re#ult of di#tri uted o!ner#hip. Standard# are thin li e: #i3e of data field# ,5 or I di&it 3ip code#' a re)iation# u#ed ,AD. or AD . for a)enue' timin& of chan&e# ,!hen do %ou clo#e the oo #' !ho can acce## data and !hen'



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ho! do %ou name data field#' ho! do %ou calculate accountin& di#count#' !hat operatin& #%#tem do !e u#e , /J$ "indo!#$...'

!hat file format i# e#t ,ASC// or BC*/C' etcK

Standard# are one of the main thin that ma e a &roup of independent file#%#tem# into a corporate data a#e. Traditional file #%#tem# ha)e )er% poor ,ifan% #tandard enforcement primaril% ecau#e no one i# in char&e of the data. o rule# e2i#t$ #o %ou &et a free-for-all.

a! 'rocessingroce##in& #tandard# tell &roup# ho! and !hen to tran#form data intoinformation. /t can include the o )iou# ho! do %ou calculate accountin&di#count# ut can al#o include more &lo al 7ue#tion# li e:

!hat hard!are i# u#ed !hat #oft!are i# u#ed !hat net!or protocol i# u#ed etc.....

Traditional file #%#tem# de)elop in the a #ence of an% centrali3ed control$hence there are fe! proce##in& #tandard# enforced unle## people informall%&et to&ether or unle## there i# a #tron& pu#h from mana&ement to!ard#commonalit%.

b! StorageThe !a% data are #tored al#o re7uire# #tandard#. The o )iou# #tora&e#tandard# include:

ho! lon& are data field# !hat t%pe are the data field# !hat are %our a re)iation#

Some more #u tle #tandard# include:

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!hat ind of di# dri)e# are u#ed !hat encodin& #cheme i# u#ed i# data compre##ion or encr%ption u#ed

Traditional file a#ed #%#tem# do not &enerall% ha)e an% #tora&e #tandard# ecau#e no central control e2erted to ma e them conform.

c! $aminginall%$ namin& #cheme# are a t%pe of #tandard not often found in traditionalfile a#ed #%#tem#. Becau#e each &roup uild# their file# in i#olation$ the%!a% data are name# i# incon#i#tent. Thi# mean# that e)en if u#er# !anted to#hare data the% !ould ha)e to fi&ure out !hat it i# called fir#t. La#tdi#ad)anta&e of traditional #%#tem#...

0. # cessive costsTraditional file a#ed #%#tem# co#t more in the lon& run. The% ma% #eemcheaper !hen %ou are de)elopin& them$ ut the com ined effect of all the

pre)iou#l% #tated pro lem# e)entuall% add# up.

a! (o) programmer producti*ityAll the comple2it% of determinin& file name# and !or in& out #tandard#$ anddealin& !ith data independence pro lem# re#ult# in L>" +>* CT/D/T9. The comple2it% of tr%in& to #hare data #lo!# do!n pro&rammer#. Al#o$ if the% ha)e to rein)ent the !heel e)er% time the% do#omethin& it re#ult# in !a#ted effort. inall%$ pro&rammer producti)it% i#lo!er ecau#e much time i# #pent in maintenance ,ne2t topic .

b! E+cessi*e maintenanceLac of data independence and the infle2i ilit% of traditional #%#tem# mean#that L>TS of effort i# #pent @u#t to eep the #%#tem# !or in&. Stati#tic# #ho!that H6E to I6E of all pro&rammer effort i# #pent maintainin& e2i#tin&

pro&ram# -- not uildin& ne! #%#tem#. Thi# doe# not ad)ance the #tate of thecompan%$ @u#t eep# them e)en. )er%one #uffer# from the hi&h co#t ofmaintenance. ro&rammer# hate it ,lou#% @o $ mana&er# di#li e it ecau#e iti# not producti)e$ u#er# di#li e it ecau#e of the ac lo. BA* Thi# i# a

prime factor in lo! pro&rammer producti)it%. Can e directl% tied to lac ofdata #harin& and centrali3ed control.



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VII. Database pproach 'ros & ConsA# hinted earlier$ the data a#e approach doe# a!a% !ith the m% data #%ndrome./t collect# all data into an or&ani3ed repo#itor%. The approach rin a ne! !a% ofthin in& and #ome ne! tool# that permit the control of redundanc%$ impro)ed

fle2i ilit%$ and centrali3ed data control.

A. Pros

1. Data inte!rationor the fir#t time$ companie# ma% #ee e2actl% !hat data the% ha)e and need.Thi# #ound# #imple$ ut it i# #urpri#in& ho! man% companie# don=t no! !hatdata the% ha)e and re7uire. ?no!in& thi# can lead to #ome efficiencie# ,e.&.$!h% are !e #torin& thi# information that no one !ant#' . Allo!# #treamlinin&

of re7uirement# and #%#tem# if effort i# applied.

(. Contro$$e re %n ancyDer% o )iou#. /f %ou onl% #tore it once then %ou do a!a% !ith redundanc% andit# related pro lem#. 2ample: /f %ou onl% #tore an emplo%ee addre## in one

place then a #in&le update i# effecti)e for all u#er#. 9ou cannot &et rid of ALLredundanc%. There are time# !hen it i# a &ood idea to eep redundant data,"e=ll tal a out that later in the #eme#ter $ ut %ou can minimi3e it. Thi# ha# a#ide enefit of #a)in& di# #pace and re7uirin& fe!er maintenance pro&ram#.

-. Data sharin!Since it i# onl% #tored in one place$ %ou mu#t #hare it. Actuall%$ #harin& i# a)er% important ad)anta&e on it# o!n. /t mean# that %ou trul% are mana&in&%our data and treatin& it li e a compan% a##et. (o!e)er$!hen data are #hared$it rin on #ome ne! pro lem# not pre#ent in traditional #%#tem#. Li econcurrenc% control. "e=ll tal a out that later.

/. Data inte!rity/nte&rit% refer# to the pro lem of incon#i#tent data in file a#ed #%#tem#. /f data

redundanc% i# reduced then data i# onl% #tored in one place$ #o the multipleincon#i#tent )er#ion pro lem i# fi2ed.

/nte&rit% i# the a##urance that the data are:

accurate

complete



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timely

reliable

/t al#o deal# !ith the notion that the data accuratel% repre#ent# the real !orld#%#tem it attempt# to model. /n other !ord#$ inte&rit% i# concerned !itho )iou# thin li e:

name# #pelled correctl% proper account num er all #ocial #ecurit% num er# are uni7ue

And al#o concerned !ith le## o )iou# thin li e: cu#tomer di#count applied to proper cu#tomer emplo%ee doe# not ma e more mone% than their o##

*ata inte&rit% i# a )er% important part of a *BMS ,and a part that mo#t do notdo )er% !ell .

0. Stan ar s enforcementStandard# enforcement i# an important ,and often i&nored part of the data a#eapproach. Since %ou ha)e centrali3ed control of data it i# ea#ier to enforce#tandard#. or e2ample:

namin& #tandard# ,e.&.$ fir#t ; character# i# #%#tem name field definition #tandard# ,MMG**G99 for date# u#a&e #tandard# ,no pa%roll data acce## on !ee end# proce##in& #tandard# ,common encr%ption al&orithm etc...

The *BA i# the per#on,# re#pon#i le for #tandard enforcement. /f the% do athrou&h @o then the data a#e if much more u#a le.

2. Centra$i3e contro$Centrali3ed control i# #ort of a #ide enefit of the data a#e approach ,not thedirect rea#on for u#in& the approach$ ut a #ide effect. Mo#t of the enefit# of



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centrali3ed control are them#el)e# ad)anta&e# of the data a#e approach.Centrali3ed control pro)ide# #ome enefit# that %ou mi&ht not immediatel%thin of. or in#tance$ 1#t enefit of centrali3ed control...

a! Security,'ri*acy9ou can etter control data #ecurit% and pri)ac% if %ou ha)e centrali3edcontrol. Securit% i# the a##urance that data i# ept from unauthori3ed u#er#.ri)ac% i# the a##urance that data i# not mi#u#ed % tho#e u#er#. ,Similarconcept#$ ut the% are not identical (a)in& all the data in one #pot !ithin theconceptual model ma e# thi# ea#ier.

b! #ntegrity#ntegrity accurate$ complete$ timel%$ relia le

A# mentioned efore$ inte&rit% i# much ea#ier if %ou ha)e a centrali3ed od%in char&e of the data and the #tandard#. Traditional file #%#tem# de)elopedinte&rit% throu&h con#i#tent &ood pro&rammin& practice# and )oluntar%cooperation amon& department#. Thi#$ in part$ e2plain# !h% #ome companie#!ere more #ucce##ful at #%#tem inte&ration than other# u#in& #imilare7uipment and doin& #imilar proce##in& ,i.e.$ the informal net!or !a#

etter .

c! ackup,Reco*ery

Bac up and reco)er% are often not done properl% in file a#ed #%#tem# ecau#e the% are not thou&ht of a# nece##ar%. ,Amateur #%#tem# mana&er#don=t reali3e the importance of ac up#. /ronicall%$ ac up# are a out themo#t important thin& that %ou can do. "hen department# handled their o!ndata$ traditional a#ed ac up and reco)er% !a# done in a #pott% andincon#i#tent manner. Some people !ere &ood at it and other# !ere not. Therea#on that more pro lem# did not occur !a# ecau#e companie# u#uall% onl%had 1 computer center ,for all their independent file- a#ed #%#tem# . Thecomputer center handled ac up and reco)er% !ithout the department=#no!led&e. Bac up and reco)er% are much ea#ier !hen data a#e method#u#ed ecau#e the *BMS can handle the detail# ,con#i#tentl% .

4. 5$e ibi$ity67esponsivenessThe data a#e approach i# much more fle2i le ecau#e %ou can acce## data!ithout concern !ith !here or ho! it i# #tored. Thi# idea i# )er% clo#e to theidea of data independence. Some oo # al#o mention that data a#e #%#tem#

pro)ide multiple retrie)al path# to each data item. Thi# i# true , ut mi##e# the

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prime point a out data independence . B% default$ a fle2i le #%#tem i# al#ore#pon#i)e. That i#$ %ou can ma e chan&e# more 7uic l% ecau#e there i# le##to chan&e. ,Le## detail to !orr% a out . Specificall%$ the fle2i ilit% of thedata a#e approach help# !ith...

a! Ad %oc &ueriesuer% lan&ua&e# ha)e een de)eloped that non- pro&rammer# can u#e to ma eone-time-onl% 7uerie# ,ad hoc . /n thi# !a% the% can #ati#f% their uni7ueinformation need# !ithout u#in& traditional pro&rammin& #er)ice# ,i.e.$ a)oidthe ac lo& . >* (o!e)er$ it #till doe# not fi2 the pro lem !here u#er#mu#t ha)e in-depth no!led&e of data name# and !here it i# #tored. 4th&eneration lan&ua&e# ,!hich i# !hat mo#t *BMS 7uer% tool# are help$ utnot 7uite a# &ood a# the #ale# literature promi#e#.

b! Multiple user *ie)sA #ide enefit of the data a#e approach i# called )ie!# . A )ie! i# a #in&leu#er# per#pecti)e of the data a#e. Briefl%$ u#er# do not need to #ee the !holedata a#e. The% t%picall% onl% need to #ee a #mall portion ,the #ame portionthat the traditional file !ould ha)e &i)en . 9ou define thi# data a#e #u #et!ith the *BMS mechani#m called )ie! definition . ,"e=ll do thi# later.Die!# enhance fle2i ilit% ecau#e the% ha)e &reat data independence. 9oucan modif% the underl%in& data !ithout di#tur in& the )ie! and chan&e the)ie! definition !ithout modif%in& the pro&ram# that u#e it ,!ith onee2ception -- %ou canNt remo)e data that the pro&ram directl% u#e# .

8. Data In epen enceTraditional pro&rammin& uild# the data definition and the data proce##in& intothe #ame unit ,called a pro&ram . Thi# mean# that !hene)er the data definitionchan&e#$ %ou ha)e modif% each pro&ram that u#e# it. BA* The data a#eapproach #eparate# the data definition and the data acce## method# from the

pro&ram# that proce## the data. Thi# pro)ide# data independence ,that i# thea ilit% to chan&e the data #tructure !ithout modif%in& pro&ram# that u#e thedata .

9. Cost savin!sThe data a#e approach #a)e# mone% in the lon& run. (o!e)er$ a# !e !ill #eelater$ a &ood *BMS i# e2pen#i)e$ #o thi# enefit i# !ea and a little harder to

pro)e.



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a! Easier application de*elopmentMuch of the !or in traditional application de)elopment i# definin& the dataand !ritin& code to acce## it. Al#o$ a &ood deal of traditional application

pro&ram# !ere de)oted to inte&rit% chec #. The data a#e approach minimi3e#

thi# ecau#e the data are alread% defined and the acce## i# up to the *BMS.Al#o$ the inte&rit% con#traint# can e uilt into the *BMS. Thi# #peed# upapplication de)elopment. (o!e)er$ it #lo!# do!n anal%#i# and uildin& time

ecau#e %ou ha)e to do all that !or up front. , o free lunche# . Code re-u#ei# another ad)anta&e of the data a#e approach. /n #ome #%#tem#$ %ou can uild&eneric routine# and ha)e the *BMS #tore them for later re-u#e. o need torein)ent the !heel and te#t the#e routine# once %ou no! the% !or . Thi#idea !a# common in traditional file- a#ed #%#tem# al#o$ ut i# ea#ier indata a#e approach.

b! Reduced maintenanceSince the data$ the data definition$ and the application pro&ram# in a *BMSare all independent$ %ou can chan&e an% !ithout affectin& the other# ,dataindependence . Thi# ma e# pro&ram maintenance ,and te#tin& ea#ier and7uic er ,le## mone% . >ld-#t%le #%#tem# forced the pro&rammer to econcerned !ith #ide effect# ,unplanned effect# of a pro&ram chan&e . /tre7uired e2ten#i)e plannin& and te#tin& for e)en #imple modification# , i& O .The data a#e approach doe# not totall% do a!a% !ith the pro lem ofmaintenance #ide effect#$ ut at lea#t it minimi3e# them. The end effect i#

etter pro&rammer producti)it%.B. ConsThi# #eme#ter !e !ill not d!ell on the pro lem# of the data a#e approach. Thead)anta&e# of data a#e &reatl% out!ei&h the pro lem#. (o!e)er$ / !ant %ou toha)e a reali#tic )ie! of *BMS from thi# cour#e ,!e are not #ellin& *BMS#here.

1. Specia$i3e personne$ an har +areAlthou&h the data a#e approach i# cheaper in the lon& run due to impro)ed

pro&rammer producti)it% ,and other rea#on# $ it ha# #ome up- front co#t# thatare not tri)ial. The#e co#t# are often o)erloo ed % an2iou# u#er#. 9ou don=t!ant to e #urpri#ed.

a! D A. DA.////f %ou plan on u#in& e2i#tin& people$ %ou !ill ha)e to #end them to trainin&cla##e# on %our *BMS product. The#e cla##e# co#t et!een OF66 to OI66 a



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da% ,plu# e2pen#e# . Cla##e# can la#t !ee #. 9ou can al#o do on-#ite trainin&$ ut that i# al#o )er% e2pen#i)e. /f %ou !ant to hire people alread% trained$the% co#t more than normal pro&rammer# , ecau#e the% ha)e had the trainin&cla##e# or e2perience . ither !a%$ %ou cannot a)oid the trainin& co#t and#u #e7uent lo## of producti)it% !hile the% learn. /n addition$ %ou !ill ha)e tohire ,or train a data a#e admini#trator ,*BA . Thi# i# a )er% #peciali3ed

per#on ,or &roup of people and the% are not cheap. ,O56$666 to O156$666 per%ear normall%.

b! C'". RAM. Disk A# far a# hard!are i# concerned$ %ou !ill pro a l% ha)e to up&rade %ourC $ u% more fa#t +AM$ and u% more di# dri)e#. Thi# co#t# i& O. Thi#i# in addition to the co#t of the *BMS it#elf. ,The% t%picall% co#t et!eenO15$666 and O166$666 ,or more .

c! 'otentially slo)er>nce the% #pend all thi# mone%$ man% are #urpri#ed that the o)erall #%#temthrou&hput i# #lo!er than !ith their old file- a#ed #%#tem ,e)en !ith the

eefed up C . The rea#on for thi# i# that the machine i# ha)in& to do a lotmore thin ,e.&.$ concurrenc% control$ #ecurit%$ inte&rit%$ reco)er%$ ... . 9ou!ant the#e thin$ it i# @u#t that people are #urpri#ed that the% #lo! do!n themachine. The real &ain in *BMS come# in

pro&rammin& co#t #a)in

etter data con#i#tenc%data #harin& #%ner&%.

(. Data conc%rrency prob$emsAlon& !ith the ad)anta&e# of data #harin& come #e)eral pro lem#. The#e

pro lem# are uni7ue to #%#tem# that allo! more than one functional area to u#ethe #ame data at the #ame time.

a! Deadlock,(i*elock

"hen data are #hared$ the *BMS mu#t e careful to onl% allo! one u#er at atime to chan&e it. /f multiple u#er# could chan&e at the #ame time then it!ould e chao#. The *BMS doe# thi# % &i)in& #ole acce## to update data toone u#er at a time. An% od% el#e that need# it mu#t !ait until the fir#t i#throu&h. *eadloc i# a condition !here ,or more u#er# are each !aitin& forthe other to relea#e the #ame piece of data. either can continue until theother &i)e# up the needed data. *eadloc ,a. .a. deadl% em race !ill

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continue until %ou turn the computer off or until one of the u#er# &i)e# in .or e2ample$ ima&ine a 4-!a% #top #i&n !ith t!o car# !aitin& for each other.

Traditionall% the *BMS loo # for deadloc and force# one u#er to relea#etheir data and #tart o)er.

Li)eloc i# a condition !here a u#er cannot proceed for a lon& time ecau#ethe% are ne)er &i)en acce## to needed data. Thi# i# different from deadloc inthat the% do not ha)e an%thin& that an%one el#e !ant#. The% are @u#t lo! onthe priorit% li#t #o the% ne)er &et acce## to a popular piece of data. A&ain$the *BMS ha# !a%# to fi2 thi# pro lem. Both pro lem# are directl% related todata #harin& ,and u#e lot# of C c%cle# .

b! Transaction Rollback >ne !a% the *BMS fi2e# deadloc i# throu&h tran#action roll ac .Ba#icall%$ a roll ac i# the proce## of undoin& e)er%thin& that a u#er ha#done. ,A tran#action i# an ar itrar% unit of !or on the data a#e. "henthe *BMS #elect# a )ictim $ the% *> e)er%thin& that u#er ha# done,includin& relea#in& loc # on data item# . >nce thi# i# done then other u#er#can continue. +oll ac # u#e lot# of C c%cle# al#o and are normall% re#ult ofdata contention ,)ia data #harin& .

-. Data sec%rity prob$ems>ne of the fe! area# !here the traditional approach !a# etter. "hen %ou

com ine all the traditional file- a#ed #%#tem# %ou al#o com ine all the #ecurit%concern# of that data. Stran&el% enou&h$ the traditional file a#ed approach hadfairl% &ood #ecurit% ecau#e people &uarded their data )er% carefull%. Some ofthe #ecurit% pro lem# are not ne! ,e.&.$ ac upGreco)er%$ authori3ation . The%are @u#t i&&er. >ther pro lem# #prin& up #pecificall% ecau#e a *BMS i#

pre#ent. or e2ample$ the potential for cata#trophic failure. All in all$ *BMS#ecurit% i# not ne!$ @u#t more inten#e.

a! Catastrophic ailure"hen %ou put all %our e& in one a# et$ %ou ri# lo#in& them. Tran#lation:Lac of redundanc% can ea#il% lead to lo#in& e)er%thin& if %ou are notcareful. ot onl% are the data not redundantl% #tored$ ut the proce##in& i#al#o performed on #in&le #et of hard!are. *an&erou# "hen %ou depend onone #%#tem ,*BMS to perform all data retrie)al$ #tora&e$ ac upGreco)er%$inte&rit%$ ... then %ou are )er% )ulnera le to a failure of that #%#tem. >n a le##cata#trophic note$ a #in&le ad application can #ometime# rin& do!n the!hole *BMS. Thi# #ort of thin& rarel% happened on old file- a#ed #%#tem#.

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b! Elaborate backup,reco*eryThi# &enerall% come# under the headin& of #ecurit%. 9ou can pro)ide ac uptape#$ ac up di# #$ ac up C #$ ... all the !a% up to totall% redundant #ite#.The more #ecurit% %ou u%$ the more it co#t#. Thi# i# not reall% that different

from file- a#ed #%#tem# #ince mo#t of the i& one# ran at a #in&le hard!are#ite. The pro lem i# that all u#er# are do!n !hen %ou do ac up#$ not @u#t afe! function#. , ote$ #ome fanc% *BMS#$ li e >+ACL $ do incremental

ac up# #o that u#er# are not o)erl% incon)enienced.

/. Or!ani3ationa$ conf$ictShared data a#e re7uire# a con#en#u# on data definition and o!ner#hip. Thi# i#!here the *BA reall% earn# their mone%. /t ta e# a &ood politician to na)i&atethi# minefield. Thi# i# a political concern. #er# from #eparate functional area#mu#t a&ree on !ho o!n# the data$ !ho can maintain it$ !hen$ ho! it i#

proce##ed$ di#tri uted$ .normall% te2t oo # minimi3e the political a#pect# ofdata proce##in& in the or&ani3ation. 9ou #hould remem er that politic# al!a%#follo!# lar&e ud&et# and po!er. Thi# i# true in the * area.

0. Comp$e concept%a$ esi!n/t i# more comple2 to under#tand ,and pro&ram !hen %ou mu#t e concerned!ith the entire enterpri#e model. *BMS pro&rammer# mu#t e concerned !ithtran#action interaction$ timin&$ and a ho#t of pro lem# not pre#ent in old file-

a#ed #%#tem#. To #ol)e thi#$ fe! companie# actuall% ha)e a full enterpri#emodel. Mo#t ha)e #u #et# of the model that lin lo&icall% related #u -#%#tem#.Thi# i# a practical !a% to approach e2treme comple2it%. /t i# not nece##aril%&ood$ it i# @u#t the !a% thin are until !e ha)e etter tool# to help the

pro&rammer deal !ith e2treme detail. ,e.&.$ CAS tool#$ S #$ ...

2. # tra costs(a)in& a *BMS in place can #lo! do!n certain a#pect# of the #%#tem life-c%cle. /f %ou e)er e)aluate a *BMS$ %ou #hould reali3e thi#.

a! Testing di iculties

9ou u#uall% cannot te#t application# directl% a&ain#t the li)e data a#e ecau#eit ma% dama&e it ,a&ain$ all e& in one a# et... . Thi# mean# that %ou mu#teither ma e an e2tract of the full data a#e or de)elop a #u -#et of the data a#e#trictl% for te#tin& purpo#e#. Thi# ta e# time and di# #pace. /t al#o ma% notade7uatel% te#t the pro lem# that often occur under load ,multiple u#er# .



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b! Comple+ en*ironmentThi# i# related to the comple2 conceptual de#i&n and #pecial pro&rammer#topic# a o)e. Ba#icall%$ *BMS product# are more comple2 to u#e than file-

a#ed #%#tem#. /t ta e# time to learn them. Al#o$ a full enterpri#e model of a

compan% i# u#uall% too comple2 for a #in&le pro&rammer to comprehend!ithout aid# ,CAS tool#$ ... . Ta en to&ether$ %ou lo#e #ome of %our pro&rammer producti)it% ,#hort run due to the comple2it% of the *BMS. Allin all ho!e)er$ the ad)anta&e# A+ > T" /


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or&ani3ation=# data. *BA ha# the ultimate authorit% and re#pon#i ilit% foren#urin& that the data i# #ecure$ accurate$ and timel%. Specificall%$ the *BAdoe#:

uild and maintain the data dictionar% re#ol)e di#pute# a out data u#a&e$ control... de#i&n and maintain the conceptual and ph%#ical data a#e monitor data a#e for performance tunin& perform ac up# and reco)erie# etc...

Sometime# the *BA po#ition i# held % a &roup of people and #ometime# thetechnical #ide i# handled % a *ata Admini#trator ,*A !hile the political #idei# handled % the *BA.

(. Systems eve$opersThe#e are pro&rammer# that !rite the application code to meet #pecification.The% are t%picall% !ell )er#ed in the u#e of the *BMS tool# and in the functionthat the% are pro&rammin&. Seldom are #%#tem de)eloper# the #ame people thatu#e the #%#tem. Thi# partl% due to the #peciali3ed nature of the !or and partl%due to a need to pro)ide #ecurit% % #eparatin& the u#er# and the de#i&ner# of

the #%#tem.-. #n %sersinall%$ the end u#er# are tho#e that ha)e a need to acce## the data. )iou#l% thi# i# themo#t important component. There are &eneral cate&orie# of data:

actual ,real *irtual ,deri)ed



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The actual data i# #tored on di# and can e read and !ritten @u#t a# intraditional #%#tem# ,althou&h %ou don=t !orr% a out #tora&e detail# Dirtual datai# not actuall% #tored an%!here. +ather$ the deri)ation method i# #tored. "hen

%ou re7uire the information it i# created frome2i#tin& data. 2ample: mplo%ee a&e !ould not reall% e #tored in thedata a#e. +ather their irthda% and the current da% !ould e u#ed to calculateit. /n that !a% it !ould al!a%# e current. Another e2ample i# if %ou !ant a#um of a purcha#e order. The #um !ould not actuall% e on di# $ rather it!ould e calculated on the fl% .

a! Actual

b! 0irtual

(. Str%ct%re+a! data i# not reall% )er% u#eful % it#elf. 9ou cannot ha)e an% relation#hip#amon& data item# in ra! data ,@u#t a unch of data item# . "hat i# mi##in& i#the #tructure that tie# the piece# to&ether. "e !ill e !or in& !ith thi# all#eme#ter. /t i# a )er% po!erful a#pect of the *BMS approach. /t i# al#o one ofthe main comple2itie# that mu#t e dealt !ith. There are #e)eral a#ic concept#a##ociated !ith #tructure:

#tructure !ithin record #tructure et!een record# cardinalit% ,1:1$ 1: $ M: - nature of relation#hip de&ree ,ho! man% entitie# participate &enerali3ationG#peciali3ation primar% e% uni7uene## referential inte&rit% u#er defined inte&rit% rule#

A &eneric term for information a out the #tructure of data i# 1metadata1/ /ndata a#e terminolo&%$ the part of the *BMS that define# the #tructure i# calledthe 1schema1/ The #chema i# #tored in the *BMS component called the



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1catalog1 or the repo#itor%. A&ain$ !e !ill &et to mo#t of thi# later$ thi# i# @u#tan introduction. ;rd *BMS component ...

D. DBMS See al#o: Soft!are

The *ata Ba#e Mana&ement S%#tem ,*BMS i# the &eneric name for thecollection of #u - #%#tem# u#ed to create$ maintain$ and pro)ide controlled acce##to data. The% ran&e in comple2it% from #mall C-*BMS #%#tem# ,Acce##$ dBa#e/D$ + a#e... co#tin& a fe! hundred dollar# to lar&e mainframe product#,>+ACL $ /BM *B co#tin& #e)eral hundred thou#and dollar#.

The central component of the *BMS. A module that pro)ide# acce## to the ph%#ical #tructure and the data. Al#o coordinate# all of the other function# done % the *BMS. The central control module that recei)e# re7ue#t# from u#er# $determine# !here the data i# and ho! to &et it$ and i##ue# ph%#ical /G> re7ue#t# tothe computer operatin& #%#tem. Al#o pro)ide# #ome mi#c. #er)ice# #uch a#memor% and uffer mana&ement$ inde2 maintenance$ and di# mana&ement.

1. DBMS #n!ine

(. Interface s%bsystemro)ide# facilitie# for u#er# and application# to acce## the )ariou# component#of the *BMS. Mo#t *BMS product# pro)ide a )ariet% of lan&ua&e# andinterface# to #ati#f% the different t%pe# of u#er# and the different #u -#%#tem#that mu#t e acce##ed. The follo!in& are common interface# that are pro)ided,#ome are mi##in& in the #mallerGcheaper product# . ote that #ome *BMScom ine the function# of #e)eral interface# into a #in&le #u -#%#tem ,e.&.$ S Li# **L$ *ML$ and *CL com ined .

a! DD(#ed to define and maintain the data a#e #tructure# ,e.&.$ record#$ ta le#$ file#$)ie!#$ inde2in&$ ... Specificall% **L define#:

all data item# ,t%pe$ #pecification...

all record t%pe# ,ta le# in relational model the relation#hip# amon& record t%pe# ,not in relational model u#er )ie!# ,or #u #chema#

The **L i# u#ed to define the conceptual data a#e and turn it into a ph%#icaldata a#e

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b! DM(#ed to manipulate and 7uer% the data it#elf. T%picall% u#ed % a ho#t

pro&ram or a# ad hoc command# in interacti)e mode. or e2ample$ %ou could#elect a #u #et of data a#ed upon #ome 7uer% criteria u#in& the *ML. /n

#ome data a#e #%#tem# the *ML al#o pro)ide# the command# to na)i&atethe data #tructure.

c! DC(#ed to &rant and re)o e acce## ri&ht# to indi)idual# ,and &roup# . A ri&hti# the pri)ile&e to perform a data manipulation operation. or e2ample$ the*BA can &rant a cler the ri&ht to acce## and delete / D T>+9 record#, ut not to update them . Another related concept i# a data a#e ProleQ. A rolei# a predefined #et of acce## ri&ht# and pri)ile&e# that can e a##i&ned to au#er. "hen the definition of the role chan&e#$ all u#er# a##i&ned to that role&et the updated acce## ri&ht#. A&ain$ not all *BMS# call the **L$ *ML$ and*CL #eparate interface#. (o!e)er$ all ; function# mu#t e pre#ent in the*BMS.

d! 2 E>ptional. Some modern *BMS# pro)ide a &raphical repre#entation of thedata #tructure ,a ta le u#uall% that allo!# %ou to #elect !hich data item# to7uer% on and the condition# for #election. ormall% thi# feature i# found inuer% B% 2ample #u -#%#tem# of relational *BMS#. The &raphic interface

ma e# it ea#ier for non- technical u#er# to ma e comple2 7uerie#. Al#o hand% ecau#e it i# a common interface that can cro## di)er#e *BMS #%#tem#.

e! 3orms inter ace>ptional. A #creen-oriented form i# pre#ented to the u#er. The% re#pond %fillin& in the lan #. The re#ult i# that the *BMS u#e# the form that %oude#i&n to input and output data.

! %i-le*el inter acero&rammer# need to e a le to acce## data )ia a hi&h-le)el lan&ua&e. Thi#

could e old-#t%le ,;rd &eneration lan&ua&e# li e C>B>L$ >+T+A $a#cal. >r it could e ne!er 4th &eneration lan&ua&e# li e Tool o2$ Mapper$a#%trie)e$ ... . Mo#t i& mainframe product# ,/n&re##$ >racle$ /nformi2...include a 4


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command# ,)er # to the #tandard lan&ua&e and ha)in& a pre-proce##ortran#late the#e )er # into *BMS call# ,u#in& the CALL format of the #pecificoperatin& #%#tem . Thi# method !or # !ell ecau#e the u#er doe# not need tono! the comple2itie# of operatin& #%#tem call# and the re#ultin& code i##ome!hat porta le. The interface# to old lan&ua&e# i# needed ecau#e therei# a lot of code and pro&rammer e2perience out there that cannot e i&nored.

-. DictionaryThe !ord repo#itor% i# u#ed to relate ac to the /nformation +e#ourceMana&ement concept mentioned earlier. The data in the data a#e #hould etreated a# a corporate re#ource. Thi# re#ource mu#t e mana&ed. Therepo#itor% i# more than a data dictionar% or catalo& . /t i# the central placethat %ou #tore:

#%#tem documentation data #tructure pro@ect life c%cle information conceptual model information etcK

CAS tool# u#e it e2ten#i)el%. A *BMS #%#tem component mu#t e pre#ent tomana&e and control acce## to the repo#itor%. To a certain e2tent$ the *CL doe#

part and CAS tool# do part. /t pro)ide# facilitie# for recordin&$ #torin&$ and proce##in& de#cription# of an or&ani3ation=# data and data proce##in&re#ource#. rett% ne! idea ,#till ein& defined % indu#tr% .

/. Data inte!rity s%bsystemThere are 4 important function#:

- intrarecord integrity - enforce con#traint# on data item )alue# and t%pe#!ithin each record in the data a#e

- re erential integrity - enforce the )alidit% of reference# et!een record# inthe data a#e

- user-de ine integrity - Bu#ine## rule# ,ar itrar% that mu#t e upheld ,e.&.$emplo%ee can=t ma e more than o## .

- concurrency control - A##urin& the )alidit% of data !hen multiple u#er#acce## #imultaneou#l% ,&et into more later .



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0. Sec%rity m!t. s%bsystemA #u #%#tem that pro)ide# facilitie# to protect and control acce## to thedata a#e. The mo#t important a#pect# of #ecurit% are:

#ecurin& data from unauthori3ed acce## protect it a&ain#t di#a#ter#

The fir#t i# done throu&h pa##!ord#$ )ie!#$ and protection le)el#. ncr%ption i#al#o !idel% u#ed. The #econd a#pect u#e# ac up#$ lo$ efore and afterima&e#$ di#a#ter reco)er% plan#$ etc.

2. Bac %p67ecoveryA #u #%#tem that lo tran#action# and data a#e chan&e# and periodicall%ma e# ac up copie# of the data a#e. Thi# i# done #o %ou don=t lo#e data in thee)ent of a pro lem. There are different le)el# of pro lem# that ac upGreco)er%

prepare# for. The% ran&e from redoin& a tran#action that !a# rolled ac due toa concurrenc% conflict ,minor to totall% re#torin& the data a#e after thecomputer center i# de#tro%ed ,ma@or .

4. pp$ication eve$opment>ptional. ro)ide# facilitie# #o that end u#er# andGor pro&rammer# can de)elopcomplete data a#e application#. Some u#e ela orate CAS tool# a# !ell a##creen and report &enerator# to create full application# !ith minimal !or .

>ther# help !rite code from # etch% #pecification#. /n an% e)ent$ thi# i# an aidto non-technical u#er# and to eef up pro&rammer producti)it%.

8. 'erformance mana!ementThe *BA need# #ome !a% to determine if the *BMS i# performin& !ell.The#e tool# ,often called monitorin& utilitie# &i)e the *BA informationneeded to tune *BMS performance. 2ample: A monitor utilit% can find dataitem# that are acce##ed fre7uentl% enou&h to need an inde2. The% can al#o eu#ed to determine if a data item need# to e on a fa#ter di# dri)e or po##i l%replicated.

. Soft!are

1. pp$ication pro!ramsThe#e are the #pecific procedure# ,pro&ram# that manipulate the data in thedata a#e. The% are !ritten for #pecific application# needed % the u#ine##.9ou don=t u% the#e a# part of the data a#e. Some are fairl% predicta le



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,pa%roll$ account# pa%a le$ &eneral led&er !hile other# could e 7uite ar itrar%and #peciali3ed. the main point i# that the% are #pecificall% !ritten for the

u#ine## u#in& u#ine## defined re7uirement#. The e#t thin& that the *BMScan do to help i# to pro)ide tool# to help !rite and maintain the pro&ram#.

(. C S# too$sComputer-Aided Soft!are n&ineerin& ,CAS tool# are u#ed for automatin&the #oft!are de)elopment and maintenance ta# #. Ba#icall%$ %ou u#e a computer

pro&ram to automate the #oft!are life-c%cle !or . Thi# i# fairl% ne! and not!idel% u#ed in indu#tr%$ ut %ou !ill ha)e #ome contact durin& %our career.*ependin& upon the CAS tool$ it can automate:

fea#i ilit% anal%#i# re7uirement# definition lo&ical de#i&n protot%pin& pro&rammin& and te#tin& implementation maintenance

/n future$ mo#t lar&e #oft!are pro@ect# !ill u#e CAS tool# ,pro a l% hoo edinto the data repo#itor% #u #%#tem . Some of the ad)anta&e# of u#in& CAStool# are:

impro)ed producti)it% in de)elopment impro)ed 7ualit% throu&h automated chec in& automatic preparation and update of documentation encoura&ement of protot%pin& and incremental de)elopment automatic preparation of pro&ram code from re7uirement# definition reduced maintenance effort#

Cop%ri&ht 0a% M. Li&htfoot$ h.*. F


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-. Operatin! system

". #ard!are

I;. Chapter

Chapter 1 Database Systems

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