MIS 385/MBA 664 Systems Implementation with DBMS/ Database ManagementChapter 9 – Client-Server EnvironmentClient/Server SystemsApplication Logic in C/S SystemsClient/Server ArchitecturesFile Server ArchitectureFile server architectureTwo-Tier ArchitectureAdvantages of Two-Tier ApproachAdvantages of stored proceduresTwo-tier architectureThree-Tier ArchitecturesThree-tier architectureAdvantages of Three-Tier ArchitectureApplication PartitioningCommon Logic DistributionsRole of the MainframeMiddlewareTypes of MiddlewareDatabase MiddlewareClient/Server SecurityKeys to Successful Client-Server ImplementationBenefits of Moving to Client/Server ArchitectureUsing ODBC to Link External Databases Stored on a Database ServerODBC ArchitectureMIS 385/MBA 664Systems Implementation with DBMS/Database ManagementDave [email protected] (email)http://www.davesalisbury.com/ (web site)Chapter 9 – Client-Server EnvironmentDefinition of termsList advantages of client/server architectureExplain three application components: presentation, processing, and storageSuggest partitioning possibilitiesDistinguish between file server, database server, 3-tier, and n-tier approachesDescribe and discuss middlewareExplain database linking via ODBC and JDBCClient/Server SystemsNetworked computing modelProcesses distributed between clients and serversClient–Workstation (usually a PC) that requests and uses a serviceServer–Computer (PC/mini/mainframe) that provides a serviceFor DBMS, server is a database serverApplication Logic in C/S SystemsGUI InterfaceProcedures, functions,programsDBMS activitiesProcessing LogicI/O processingBusiness rulesData managementStorage LogicData storage/retrievalPresentation LogicInput–keyboard/mouseOutput–monitor/printerClient/Server ArchitecturesFile Server ArchitectureDatabase Server ArchitectureThree-tier ArchitectureClient does extensive processingClient does little processingFile Server ArchitectureAll processing is done at the PC that requested the data – fat client Entire files are transferred from the server to the client for processingProblems:Huge amount of data transfer on the networkEach client must contain full DBMS Heavy resource demand on clientsClient DBMSs must recognize shared locks, integrity checks, etc.FAT FAT CLIENTCLIENTFile server architectureTwo-Tier ArchitectureClient is responsible for I/O processing logic Some business rules logicServer performs all data storage and access processing  DBMS is only on serverAdvantages of Two-Tier ApproachClients do not have to be as powerfulGreatly reduces data traffic on the networkImproved data integrity since it is all processed centrallyStored procedures  DBMS code that performs some business rules done on serverAdvantages of stored proceduresCompiled SQL statementsReduced network trafficImproved securityImproved data integrityThinner clientsThinner Thinner clientsclientsDBMS only DBMS only on serveron serverTwo-tier architectureThree-Tier ArchitecturesThin Client – PC just for user interface and a little application processing. Limited or no data storage (sometimes no hard drive)GUI interface (I/O processing)BrowserBusiness rulesWeb ServerData storageDBMSClientClientApplication serverApplication serverDatabase serverDatabase serverThinnest Thinnest clientsclientsBusiness rules on Business rules on separate serverseparate serverDBMS only on DBMS only on DB serverDB serverThree-tier architectureAdvantages of Three-Tier ArchitectureScalabilityTechnological flexibilityLong-term cost reductionBetter match of systems to business needsImproved customer serviceCompetitive advantageReduced riskApplication PartitioningPlacing portions of the application code in different locations (client vs. server) AFTER it is writtenAdvantagesImproved performanceImproved interoperabilityBalanced workloadsCommon Logic DistributionsProcessing logic could be at client, server, or both Processing logic will be at application server or Web serverRole of the MainframeMission-critical legacy systems tend to stay on mainframes Client/server systems tend to be small workgroup systemsProblems moving mission critical systems from mainframe to distributedDetermining which code belongs on server vs. clientIdentifying potential conflicts with code from other applicationsEnsuring sufficient resources exist for anticipated loadRule of thumbMainframe for centralized data that does not need to be movedClient for data requiring frequent user access, complex graphics, and user interfaceMiddlewareSoftware that allows an application to interoperate with other softwareNo need for programmer/user to understand internal processingAccomplished via Application Program Interface (API)The “glue”“glue” that holds client/server applications togetherTypes of MiddlewareRemote Procedure Calls (RPC) client makes calls to procedures running on remote computerssynchronous and asynchronousMessage-Oriented Middleware (MOM) asynchronous calls between the client via message queuesPublish/Subscribepush technology  server sends information to client when availableObject Request Broker (ORB)object-oriented management of communications between clients and serversSQL-oriented Data Accessmiddleware between applications and database serversDatabase MiddlewareODBC–Open Database ConnectivityMost DB vendors support thisOLE-DBMicrosoft enhancement of ODBCJDBC–Java Database ConnectivitySpecial Java classes that allow Java applications/applets to connect to databasesClient/Server SecurityNetwork environment  complex security issuesSecurity levels:System-level password securityfor allowing access to the systemDatabase-level password securityfor determining access privileges to tables; read/update/insert/delete privilegesSecure client/server communication via encryptionKeys to Successful Client-Server ImplementationAccurate business problem analysisDetailed architecture analysisArchitecture analysis before choosing toolsAppropriate scalabilityAppropriate placement of servicesNetwork analysisAwareness of hidden costsEstablish client/server securityBenefits of Moving to Client/Server ArchitectureStaged delivery of functionality speeds deploymentGUI