Lecture Notes Unit3 chapter20 - Database System Architectures

Description:
Welcome to the comprehensive guide on Relational Database Management System (RDBMS) concepts, tailored for final year B.Sc. Computer Science students affiliated with Alagappa University. This document covers fundamental principles and advanced topics in RDBMS, offering a structured approach to understanding databases in the context of modern computing. PDF content is prepared from the text book databse system concepts by siberschatz, Korth and sudharsan

Key Topics Covered:

Main Topic : Database System Architectures
Sub-Topic :
Client Server Database System, Parallel database system, distributed database processing system, Centralised, client-server architectures , Network type, local area network, wide area network
Target Audience:
Final year B.Sc. Computer Science students at Alagappa University seeking a solid foundation in RDBMS principles for academic and practical applications.

URL for previous slides
Unit 2:
https://www.slideshare.net/slideshow/lecture-notes-unit2-chapter7-relationaldatabasedesign/271859844
Unit I:
Chapter 6 : Database Design and ER Model https://www.slideshare.net/slideshow/lecture-notes-unit-1-chapter-6-e-r-model/271813542
Chapter 1 : Introduction to DBMS
https://www.slideshare.net/slideshow/lecture-notes-unit1-chapter1-introduction/271392881

Unit V
Chapter 20:
https://www.slideshare.net/slideshow/lecture-notes-unit5-chapter20-transaction/270998760
Chapter 19:
https://www.slideshare.net/slideshow/lecture-notes-unit5-chapter19-cursor-in-pl-sql/270998251
Chapter 18: https://www.slideshare.net/slideshow/lecture-notes-unit5-chapter18-packages-pdf/270845026
Chapter 17: https://www.slideshare.net/slideshow/lecture-notes-unit5-chapter17-stored-procedures-and-functions/270844763
Chapter 16 : https://www.slideshare.net/slideshow/lecture-notes-unit5-chapter16-trigger-creation/270631080
Chapter 15 : https://www.slideshare.net/slideshow/lecture-notes-unit5-chapter-15-pl-sql-programming/270383949

Unit IV

Chapter 14 Synonym : https://www.slideshare.net/slideshow/lecture_notes_unit4_chapter14_synonyms-pdf/270327685
Chapter 13 Users, Privileges : https://www.slideshare.net/slideshow/lecture-notes-unit4-chapter13-users-roles-and-privileges/270304806
Chapter 12 View : https://www.slideshare.net/slideshow/rdbms-lecture-notes-unit4-chapter12-view/270199683
Chapter 11 Sequence: https://www.slideshare.net/slideshow/sequnces-lecture_notes_unit4_chapter11_sequence/270134792
chapter 8,9 and 10 : https://www.slideshare.net/slideshow/lecture_notes_unit4_chapter_8_9_10_rdbms-for-the-students-affiliated-by-alagappa-university/270123800

About the Author:
Dr. S. Murugan is Associate Professor at Alagappa Government Arts College, Karaikudi. With 23 years of teaching experience in the field of Computer Science, Dr. S. Murugan has a passion for simplifying complex concepts in database management.

Disclaimer:
This document is intended for educational purpose.

1. RDBMS -Unit III
Chapter 20
Database System Architectures
Prepared By
Dr.S.Murugan, Associate Professor
Department of Computer Science,
AlagappaGovernmentArts College, Karaikudi.
(Affiliated by AlagappaUniversity)
Mailid: [email protected]
Reference Book:
Database System Concepts by Abraham Silberschatz, Henry
F.Korth, S. Sudharshan

2. Database System Architectures –Client Server Database System
➢Networkingofcomputersallowssometaskstobe
executedonaserversystemandsometaskstobe
executedonclientsystems.
➢Thisdivisionofworkhasledtoclient-serverdatabase
systems.

3. Database System Architectures –Parallel Processing System
➢Parallelprocessingisamethodofsimultaneously
breakingupandrunningprogramtasksonmultiple
microprocessors,therebyreducingprocessingtime.
➢Parallelprocessingmaybeaccomplishedvia
acomputerwithtwoormoreprocessorsorviaa
computernetwork.
➢Parallelprocessingisalsocalledparallelcomputing

4. Database System Architectures –Parallel Processing System

5. Database System Architectures –Distributed Data Processing System
➢Distributeddataprocessingisacomputer-networking
methodinwhichmultiplecomputersacrossdifferent
locationssharecomputer-processingcapability.

6. 2O.1 CentraIizedand Client -Server Architectures
➢Amodern,general-purposecomputersystemconsists
ofonetoafewCPUsandanumberofdevice
controllersthatareconnectedthroughacommonbus
thatprovidesaccesstosharedmemoryasshownin
Figure20.1.

7. 2O.1 CentraIizedand Client -Server Architectures
➢Acomputersystemmaybesingleuserormultiuser.
➢Atypicalsingle-usersystemisadesktopunitusedby
asingleperson,usuallywithonlyoneCPUandoneor
twoharddisks,andusuallyonlyonepersonusingthe
machineatatime.
➢Atypicalmultiusersystem,ontheotherhand,has
moredisksandmorememory,mayhavemultiple
CPUsandhasamultiuseroperatingsystem.
➢Itservesalargenumberofuserswhoareconnectedto
thesystemviaterminals.

8. 20.1.2 Client-Server Systems
➢Thecentralizedsystemstodayactasserversystems
thatsatisfyrequestsgeneratedbyclientsystems.
Figure20.2showsthegeneralstructureofaclient-
serversystem.

9. 20.1.2 Client-Server Systems
➢Thefunctionofdatabasecanbebroadlydividedinto
twoparts.Oneisfront-endandanotheroneisBack-
endasshowninFigure20.3.
➢Thefront-endofadatabasesystemconsistsoftools
suchasSQLuserinterface,formsinterfaces,report
Generation.
➢Thebackendmanagesaccessstructuresandquery
Evaluation.
➢Theinterfacebetweenthefrontendandthebackend
isthroughSQL,orthroughanapplicationprogram.

10. 20.1.2 Client-Server Systems

11. 2O.2 Server System Architecture
➢Serversystemscanbebroadlycategorizedas
transactionserversanddataservers.
➢Transaction-serversystems,alsocalledquery-
serverwhichreceivestheanswerfromtheserver
basedontheclientrequest.
➢Data-serversystemsallowclientstointeractwiththe
serversbymakingrequeststoreadorupdatedata.

12. 20.2.1 Transaction-Server Process Structure
➢Atransaction-serversystemconsistsofmultiple
processesaccessingdatainsharedmemory,asin
Figure20.4.Theprocessesthatformpartofthe
databasesysteminclude.
➢Serverprocesses:Theseareprocessesthatreceiveuser
queries(transactions),executethem,andsendthe
resultsbacktotheclient.
➢Lockmanagerprocess:Itincludeslockgrant,lock
release,anddeadlockdetection.

13. 20.2.1 Transaction-Server Process Structure
➢Databasewriterprocess:Theoutputcanbestored
fromspoolintoharddiskanduserrecords.
➢Logwriterprocess:outputslogrecordsfromthelog
recordbuffertostablestorage.
➢Processmonitorprocess:Ittakesrecoveryactions.

14. 20.2.1 Transaction-Server Process Structure

15. 2O.2 Server System Architecture
➢Data-serversystemsareusedinlocal-areanetworks,
wherethereisahigh-speedconnectionbetweenthe
clientsandtheserver,theclientmachinesare
comparableinprocessingpowertotheserver
machine,andthetaskstobeexecutedarecomputation
intensive.
➢Insuchanenvironment,itmakessensetoshipdatato
clientmachines,toperformallprocessingattheclient
machine(whichmaytakeawhile),andthentoship
thedatabacktotheservermachine.
➢Notethatthisarchitecturerequiresfullback-end
functionalityattheclients.
➢Data-serverarchitectureshavebeenparticularly
popularinobject-orienteddatabasesystems.

16. 2O.3 Parallel Systems
➢ParallelsystemsimproveprocessingandI/Ospeeds
byusingmultipleCPUsanddisksinparallel.
➢Inparallelprocessing,manyoperationsareperformed
simultaneously,asopposedtoserialprocessing,in
whichthecomputationalstepsareperformed
sequentially.
➢Acoarse-grainparallelmachineconsistsofasmall
numberofpowerfulprocessors.
➢Amassivelyparallelorfine-grainparallelmachine
usesthousandsofsmallerprocessors.

17. 2O.3 Parallel Systems
Therearetwomainmeasuresofperformanceofa
databasesystem:
(1)throughput,thenumberoftasksthatcanbe
completedinagiventimeinterval,and
(2)responsetime,theamountoftimeittakesto
completeasingletaskfromthetimeitissubmitted.

18. 20.3.1 Speedup and Scaleup
➢Twoimportantissuesinstudyingparallelismare
speedupandscaleup.
➢Runningagiventaskinlesstimebyincreasingthe
degreeofparallelismiscalledspeedup.
➢Handlinglargertasksbyincreasingthedegreeof
parallelismiscalledscaleup.

19. 20.3.1 Speedup and Scaleup

20. 20.3.1 Speedup and Scaleup

21. 20.3.2 lnterconnectionNetworks
➢Parallelsystemsconsistofasetofcomponents
(processors,memory,anddisks)thatcancommunicate
witheachotherviaaninterconnectionnetwork
➢Figure20.7showsthreecommonlyusedtypesof
interconnectionnetworks:
(i)Bus
(ii)Mesh
(iii)Hybercube

22. 20.3.2 lnterconnectionNetworks -Bus
➢AIIthesystemcomponentscansenddataonand
receivedatafromasinglecommunicationbus.This
typeofinterconnectionisshowninFigure(a).
➢ThebuscouldbeanEthernetoraparallel
interconnect.
➢Busarchitecturesworkwellforsmallnumbersof
processors.

23. 20.3.2 lnterconnectionNetworks -Mesh
➢Thecomponentsarenodesinagrid,andeach
componentconnectstoallitsadjacentcomponentsin
thegrid.
➢Inatwo-dimensionalmesheachnodeconnectstofour
adjacentnodes,Figure(b)showsatwo-dimensional
mesh.

24. 20.3.2 lnterconnectionNetworks -Hybercube
➢Thecomponentsarenumberedinbinary,anda
componentisconnectedtoanotherifthebinary
representationsoftheirnumbersdifferinexactlyone
bit.

25. 20.3.3 Parallel Database Architectures
➢Thereareseveralarchitecturalmodelsforparallel
machines.
➢AmongthemostprominentonesarethoseinFigure
20.8(inthefigure,Mdenotesmemory,Pdenotesa
processor,anddisksareshownascylinders):

26. 20.3.3 Parallel Database Architectures
➢Sharedmemory.Alltheprocessorsshareacommon
memory(Figure20.8a).
➢Shareddisk.Alltheprocessorsshareacommonsetof
disks(Figure20.8b).Shared-disksystemsare
sometimescalledclusters.
➢Sharednothing.Theprocessorsshareneithera
commonmemorynorcommondisk(Figure20.8c).
➢Hierarchical.Thismodelisahybridofthepreceding
threearchitectures(Figure20.8d)

27. 20.3.3 Parallel Database Architectures

28. 2O.4 Distributed Systems
➢Inadistributeddatabasesystem,thedatabaseisstored
onseveralcomputers.
➢Thecomputersinadistributedsystemcommunicate
withoneanotherthroughvariouscommunication
media,suchashigh-speednetworksortelephone
lines.Thegeneralstructureofadistributedsystem
appearsinFigure20.9.

29. 2O.4 Distributed Systems
S.No.Shared Nothing
ParallelDB
Distributed DB
1. Paralleldatabasesare
not geographically
separated,notseparately
administratedandhave
afasterinterconnection.
Distributeddatabases are
geographicallyseparated,separately
administered,andhaveaslower
interconnection.
2. Thereisnodifferencein
localtransactionand
globaltransaction.
Thereisadifferencebetweenlocal
transactionandglobaltransaction.In
localtransaction,accessesdataonly
fromsiteswherethetransactionwas
initiated.
Inglobaltransaction,accessesdata
inseveraldifferentsites.

30. 2O.4 Distributed Systems
➢Distributedsystemsaredevelopedforthepurposeof
sharingdata,autonomyandavailability.
➢Sharingdata:Theusermayabletoaccessthedata
fromothersite.
➢Autonomy:Localdatabaseadministratoris
availableforeverysite.
➢Availability:Ifonesitefailsinadistributedsystem,
theremainingsitesmaybeabletocontinue
operating.

31. 20.4.1 An Example of Distributed Database
➢Considerabankingsystemconsistingoffour
branchesinfourdifferentcities.
➢Eachbranchhasitsowncomputer,withadatabaseof
alltheaccountsmaintainedatthatbranch.
➢Therealsoexistsonesinglesitethatmaintains
informationaboutallthebranchesofthebank.
➢Eachbranchmaintainsarelationaccount
(Account_schema),where
Account_schema=(account_number,branch_name,ba
lance)

32. 20.4.1 An Example of Distributed Database
➢Thesitecontaininginformationaboutallthe
branchesofthebankmaintainsthereIationbranch
(Branch_schema),where
Branch_schema=(branch_name,branch_city,assets)
➢Ifthedatawereaccessedfromsinglesiteforthe
transactioniscalledlocaltransaction.Forex,fund
transferfromAccountAtoAccountBinthesame
branchwiththesamecity.
➢Ifthedatawereaccessedfrommultiplesiteforthe
transactioniscalledglobaltransaction.Forex,fund
transferfromAccountAtoAccountBinthesame
branchwiththedifferentcity.

33. 20.4.2 lmplementationlssues
➢Atomicityoftransactionsisanimportantissuein
buildingadistributeddatabasesystem.
➢Ifatransactionrunsacrosstwosites,itmaycommit
atonesiteandabortatanother,leadingtoan
inconsistentstate.
➢Thisproblemsolvedbythetwo-phasecommit
protocol(2PC).
➢Thecoordinatordecidestocommitthetransaction
onlyifthetransactionreachesthereadystateatevery
sitewhereitexecuted;otherwise(forexample,ifthe
transactionabortsatanysite),thecoordinatordecides
toabortthetransaction.

34. 20.4.2 Implementation lssues
➢Concurrencycontrolisanotherissueinadistributed
database.
➢Sinceatransactionmayaccessdataitemsatseveral
sites,transactionmanagersatseveralsitesmayneed
tocoordinatetoimplementconcurrencycontrol.
➢Iflockingisused,lockingcanbeperformedlocally
atthesitescontainingaccesseddataitems,butthere
isalsoapossibilityofdeadlockinvolving
transactionsoriginatingatmultiplesites.
➢Thereforedeadlockdetectionneedstobecarriedout
acrossmultiplesites.

35. 20.4.2 Implementation lssues
➢Theprimarydisadvantageofdistributeddatabase
systemsare:
➢Software-developmentcostishigh.
➢Greaterpotentialforbugs.
➢Increasedprocessingoverhead.

36. 2O.5 Network Types
➢Distributeddatabasesandclient-serversystemsare
builtaroundcommunicationnetworks.
➢Therearebasicallytwotypesofnetworks:local-area
networksandwideareanetworks.
S.No
.
Local Area Network Wide Area Network
1.processorsaredistributed
oversmallgeographical
areas,suchasasingle
buildingoranumberof
adjacentbuildings.
anumberofautonomous
processorsaredistributedovera
largegeographicalarea(suchas
theUnitedStatesortheentire
world)

37. 20.5.1 Local-Area Networks
➢Local-area networks (LANs) (Figure 20.10) emerged
in the early 1970s as a way for computers to
communicate and to share data with one another.

38. 20.5.1 Local-Area Networks
➢LANs are generally used in an office environment
➢LANs have a higher speed and lower error rate than
WAN
➢The most common links in a local-area network are
twisted pair, coaxial cable, fiber optics.
➢Communication speeds range from a few megabits
per second to gigabits per second.

39. 20.5.1 Local-Area Networks
➢Astorage-areanetwork(SAN)isaspecialtypeof
high-speedlocal-areanetworkdesignedtoconnect
largebanksofstoragedevices(disks)tocomputers
thatusethedata(seeFigure20.11).

40. 20.5.2 Wide-Area Networks
➢ThefirstWANtobedesignedanddevelopedwasthe
Arpanet.WorkontheArpanetbeganin1968.
➢TheArpanethasgrownfromafour-siteexperimental
networktoaworldwidenetworkofnetworks,the
Internetcomprisinghundredsofmillionsofcomputer
systems.
➢Dataratesforwide-arealinkstypicallyrangefroma
fewmegabitspersecondtohundredsofgigabitsper
second.
➢Thelastlink,toendusersites,isoftenbasedondigital
subscriberline(DSL)technologyorcablemodemor
dial-upmodem

41. 20.5.2 Wide-Area Networks
➢WANscanbeclassifiedintotwotypes:
➢IndiscontinuousconnectionWANs,suchasthose
basedonwirelessconnections,hostsareconnectedto
thenetworkonlypartofthetime.
➢IncontinuousconnectionWANs,suchasthewired
Internet,hostsareconnectedtothenetworkatalltimes.