Usng
Vlo1.9No.4Dec.2003
;UsngMiddlewaretoMigrateLegacySystem:ACaseStudy ;XingDahong(邢大红),LiuZongtian,XuDong,YangXuejun”
;(ResearchInstituteofIVli~puter,HdeiUniversityofTechnology,Hdei230009,P.R.China)
;(SchoolofComputer,shanghaiUniversity,hai200072,P.R.China) ;(“AnhuiBranchofChinaConstructionBank,Hefe230009,P.R.chi.~)
;Abstract
;erehasbeenanincreasingneedtomigratelegacysystemstonewhardwaretechnologies
;andsoftwaredevelopmentparadigmsbecausethelegacysystemspresentproblemssuchaslowef—
;fectivenessandhighmaintenance.Iforganizationswanttoremaincompetitiveintoday’sfast
;changingbusinessandtechnologicalenvironment,theymustovercometheseproblems.Middle—
;wareisflvaluabletechnologyinthatitprovidesconvenientmethodstoconstructsysteminfras—
;tructure.soitcanbeusedtomigratethelegacysystems.Thispapergivesacasestudyonusing
;middlewaretechnologiesfortheimplementationofreengineeringdistributedaridheterogeneous
;banklegacysysteminAnhuibranchofChinaConstructionBank.Usingmiddlewaretomigrate
;legacysystemhasprovedtobegoodchoiceinpractice. ;Keywords:legacysystem,middleware,migrate ;0Introduction
;Therehasbeenanincreasingneedtoreplace
;legacysystemstonewhardwaretechnologiesand ;softwaredevelopmentparadigmsbecausethelegacy ;systemspresentproblemssuchasloweffectiveness ;andhighmaintenance.Iforganizationswanttore—
;maincompetitiveintoday’sfastchangingbusiness
;andtechnologicalenvironment,theymustovercome ;theseproblems.Therearetwomainapproachestore—
;placelegacysystemstonewplatformsandprogram—
;mjngparadigms.(a)Redevelopment:Existinglega—
;cysystemsarethoroughlyanalyzedandthentrans—
;formedintocompletelynewsystems.Thisapproach ;ismorethanjustconvertingflcodefromonelanguage ;toanother.Itistheconversionofentiresystemarchi—
;tectures,includinghardwareandsystemplatform. ;Thereareseveraladvantages.Specifications,design, ;andimplementationcanbestartedwithgoodprac—
;tices.Therea1?alsoseveraldisadvantages,suchas
;highcost,timeconsumingandhighrisk.Itisinfea—
;sibleformanyorganizationstoredeveloplargelegacy ;systemsfromscratchduetounaffordablecosts,time,
;andrisksofredevelopingflreplacementsystemgiven ;theknowledgeandexpertiserecordedintheexisting ;systems.(b)Migration:Becauseorganizationshave ;alreadymadesignificantinvestmentintheirlegacy ;systems,theyareusuallywillingtoretainthelegacy ;systemfunctionalityandcauselittledisruptiontothe ;ReceivedonMay6,2003
;existingoperationalandbusinessenvironmentaspo8一
;sible.Migrationmovestheexistingoperationalsys—
;temtoflnewplatform.Keepingthecompany’slegacy
;systemsoperational,preservingthelegacysystems, ;andfacilitatingthe?mpan,
;slegacysystemsevolu—
;tionaI?majngoalsofthisapproach.Fromeconomical ;pointofview,migrationisthereforemorefeasible ;wayofmodernizingthelegacysystems.
;Therearefllotofwaystomigratelegacysystems ;tonewerparadigms.DeLuciaeta1.havedevelopedfl ;waytomigratelegacysystemstoobject—-orientedplat..
;forms….Theyusereverse-engineeringtechniquesfor
;objectidentificationatfirstandthenencapsulatethe ;identifiedobjeetsintowrappers.Finally,theyfinish ;migrationbyperformingtheincrementaltranslation ;of”legacyobjects”toobject-orientedplatforms.Sneed
;andMajnarstudyonmigratinglegacysystemstoob—
;jecttechnologiesandclient/serversystems【.They
;usewrappingatdifferentlevelsofencapsulationsuch ;asjob,transaction,program,module,andproce—
;dure.Inthispaper,wefirstlyintroducemiddleware ;intheSection1,andthengiveourstudyonusing ;mid~ewaretechnologytoachievemigrationinSec—
;tion2.
;Thetermmiddlewareisusedtodescribeflframe—
;workofgeneralservicesthatexistbetweentheappli—
;cationandthenetwork.Middlewareisflvaluable ;一
;91—
;
;Vo1.9No.4Dec.20o3
;technologyinthatitprovidesageneralmechanismfor ;distributedapplicationstocooperateusingacommon ;poolofservices.Itprovidesfunctionsoutsidethe ;realmofanapplication.Throughtheuseofapplica- ;tionprogramminginterfaces(APIs),thedeveloper
;incorporatesthemiddlewareservicesinto811applica- ;tion.Each/niddleware~viceistranstkarenttothe ;applicationinthatthemiddlewareprovidesanab—
;stractionfromitsfunctionality.Therefore,develop—
;ersconcentrateonthespecificdetailsoftheapplica—
;tionsfunctionality.reducesthecomplexityof ;building811applicationandthetimeofcreatinganap—
;plication.Generallyspeaking,mid&ewareisaninte—
;grallayerofsoftwareindistributedsystems.Ithides ;thedetailsoftheunderlyingfunctionsfromtheappli—
;cation.asweftasendusers.Programmingabstrac—
;tionsallowdeveloperstoseamlesslyblendmiddleware ;intotheirapplications.Middlewareprovidesasetof ;services,suchasidentification,authorization,direc—
;tory,andsecurity.ThesecoInnlonandreusablefunc—
;tionsassistthecooperationofdistributedapplications. ;Today,manydistributedsystemsexistina1-1en—
;vironmentofmixedhardwareandsoftwarecompo—
;nents.Moreover,themixischangingallthetimeas ;newhardwareinnovationsaremade.leitishigh—
;lydesirablethatthedevelopersofanapplicationhave ;thefreedomtochoosethecomputingplatformson ;whichtorunit.itisalsodesirabletoshieldtheappli—
;cationprogrmmnerfromthepeculiaritiesofparticular ;hardwareplatforms,andalsofromtheintricaciesof ;makingdifferentplatformsinteroperate.Middleware ;canmeettheserequirements,becauseitscomprehen—
;slvecapabilitiessupportanintegratedi~rastructure ;thatearconnectlegacysystems.So.middlewarecan ;provideaneffectivewaytomigratethelegacys~tem ;smoothly,espedallyforaheterogeneousdistributed ;environment.
;2TheCaseofMigrationofL嘤SystemUsing
;删eware
;2.1Background
;TheAnhuibranchofChinaConstructionBank
;hasusedabusinessapplicationsystemforfiveyears ;since1995.There.are’16citiesintheAnhui
;province.Everycityformeditsdatapjro0沿section,
;whichwastwo-tierclient/serverarchitecture.e ;switchcenterconnected16dataprocesscentersfor ;dataexchangebetweendifferentdataprocesscenters. ;Businessdataweredistributedin16sectionsrespec—
;tivelyandeachsectionhadadifferenthardwareplat—
;form.Thelegacysystemwasdistributedandhetero.. ;一
;92一
;geneous.asshowninFig.1.Obviously,itwasdiffi—
;cultfortheexistingsystemstobereadilyaccorflrllo—
;datedtonewcircumstances.Themfom,theintegra—
;tionandevolutionofexistingsystemsrepresentoneof ;themosturgentprioritiesofbankbusinesslegacysys—
;tems.Integrating16sectionsandconcentratingtheir ;datatoformasingleprocesscentercanimprovethe ;systeminflexibility,scalability,maintainabilityand ;reliability.Wecallthismigrationactionthedatacon—
;centrationproject.Mainobjectivesofthepectare ;keopingtheexistingsystemfunctions,makinguseof ;originalinvestmentincludinghardwareandsoftware, ;andreducingimplementingtime.
;Fig.1Legacysystemarchitecture
;2.2MigrationApproach
;2.2.1Decomposinglegacysystemfort’inhetero—
;geneousdistributedcomputingenvironments ;Weanalyzethoroughlythelegacys~temand ;takefldecomposingstrategytoutilizethelegacyre—
;sources.Decomposingaprogramentailstheidentifi—
;cationandreorganizationofdifferentprogramcompo—
;nents.Inourproject,thesoftwaresystemisdecom—
;pondintothreetypesofcomponents:userinterface ;components,applicationlogiccomponents,and ;databasecomponents.Userinterfacecomponentsin. ;eludestate~nentsthatdirectlyorindirectlycontrolthe ;executionofI/0controlstatements.Indeed.ina ;newdient/serversystem,theclientshouldmainly ;implementtheuserinterface.havecontrolofthesys. ;tern,andrequeststheservicesneeded(mainly ;databaseaccesses)fromtheserver.So,userinterface ;componentsaremigrat~totheclient.Adatabase ;componentmightbecomposedofanypieceofcode ;clusteringaroundI/0statementsonDISKfiles.in. ;eludingchunksofembeddedSQLor4GLcode.The ;databasecomponentsaremigratedtotheserver.Ap ;plicationlogiccomponentscorrespondtoaxlefrag—
;mentsimplementingbusinessrules.硒eapplication
;logiccomponentsareindependentofeachotherand ;interact,ththedatabasecomponents.Theyarealso ;migratedtoth6server.
;
;V0I.9No.4Dec.2003
;2.2.2Establishingthemiddle.re-basedstructtire ;,introducemiddlawaretotransformthelegacy ;systemintoathree-tierclient/serverarchitecturefls ;showninFig.2.Theopenarchitecture.basedonthe ;introductionoftheTlD(][Omiddlawarefromthe ;BEACompanyt4..notonlyreducestheeffortneoeS—
;saryforallowingexistingsystemstointerwork,but ;alsoeffectivelyestablishesafunctionalandinforma- ;tionalbasiseotnnlontothewholeorganization.New ;applicationscanalsoberapidlydevelopedandnatively ;integratedwiththerestofthesystem.Threetypesof ;componentsdecomposedfromthelegacysystemare ;combinedwiththenewapplicationsystem. ;Nearly900front—endterminalsinstallTlDDO
;client.16citycommunicationserversinstallboth ;TIDDOclientandserver.Thecentralcenterin—
;stallsTID)server.Onlycentralcenterbuysa ;newmainframe.Therestpartsofthenewsystemare ;ofiginalmachinel3].
;Fig.2Newsystemphysicalarchitecture
;Thefront—endinstallsapplicationsystemclient ;software,whichcombinesthelegacyuserinterface ;components.Thecentralcenterinstallssystemserver ;software,whichcombinesthelegacyapplicationlogic ;components,anddatabasecomponents.Newapplica—
;tionsoftwareisdevelopedforthedtycommunication ;servers.Thenewsoftwareworksasserverforfront- ;endandclientforthecentralcenteratthesametime. ;Therestsurroundingthemainsystem.suchastele—
;phonebanksystem,POS(PointOfSale)systemand ;ATM(AutomaticTellerMachine)system,remain ;thesameasbefore.Thesearealsothelegacysystems ;thatbelongtoeachcity.
;2.3EffectofMigration
;Ittookusnearlyoneyeartomigratealegacy ;system.Now,thenewsystemhasrunsmoothlyfor2 ;years.Thetotalcostoftheprojectwas$60million. ;Ifweconstructthenewsystemfromscratchwithout ;makinguseoflegacysystem,thetotalcostofthe ;proiectisestimatedtobe$200millionandwilltake ;2yearstoimplement.Obviously,migratingthelega—
;cysystemusingmiddlawareiscost-effective.
;3Conclusion
;Fromourstudy,themiddlewarerepresentsthe ;keyelementforensuringtheopennessandmodularity ;ofaninformationsystem.aSwellasanoperationalin ;frastructuresuitablebothfortheintegrationoflegacy ;systemsandthedevelopmentofnewmodules.There ;fore,itisgoodchoicefororganizationstomigratethe ;legacysystem.
;References
;[1]【)eLuciaA,DiLuccaG,FasolinoA,eta1.Silverspring. ;I?,EComputerSocietyPress,1997.122，129
;[2]SneedH,MajnarR.Silverspring.IE】旺ComputerSociety
;Press,1998.86，93
;[3]xingDH,WangHC.F/nanc/a/computerofChina, ;2o02,(2):52
;[4]BEASystems,Inc.Openwhitepaper.http://www.bea. ;coin
;.
;rangDahong,hornin1966.Hereceivedhis
;Master’sdegreefromHefeiUniversityofTechnolo—
;gY.NowheisaPh.D.candidateinHefeiUniversity ;ofTechnology.Hisresearchinterestsincludesoft ;warearchitecture,softwareengineering,software ;processassessmentandimprovement.
;一
;93—
;
;