Data Storage and Data Processing ArchitecturesReff : Data Management Databases and OrganizationsRichard T. Watson

Architectures

Personal databaseLocal storage and processingAdvantagesPersonal computers are cheapGreater controlDesktop OS makes PC easier to usePC users have an extensive choice of user friendly softwareDisadvantagesReplication of applications and dataDifficult to share dataSecurity and integrity are lowerDisposable systemsMisdirection of attention and resources

Remote job entryLocal storage, remote processingUseful when a personal computer is :too slowhas insufficient memorysoftware is not availableLocal storage is used for several reasons :often cheaper (if management charge for storage space in remote terminal)user still can do some local processing & data preparation such as data entry, validation & reportinguser may feel that local storage is more secure for particularly sensitive data

Host/terminalRemote storage and processingAssociated with mainframe computersAll shared resources are managed by the host (server)

Host/terminalTerminals have minimal processing capability and are used to display data and may do some limited formattingDC (Data Communications) manager handles the transfer of data between application programs and terminals

A brief overview of LANLAN connects computers within the same limited geographic areaPermits sharing of devices & dataLAN basic components include network cabling, network interface card, a file server for storing shared data, a network OSA server is a computer that provides and controls access to a shareable resource

File/serverA file/server is a LAN computer with a large disk storageFiles are stored on a file/serverData is processing on users PCEntire files are transmitted on the LANCan result in heavy LAN trafficFile is locked when retrieved for updateLimited to small files and low demand

File/server

DBMS/serverA server runs a DBMSOnly necessary records are transmitted on the LANLess LAN traffic than file/serverBack-end program on the server handles retrievalFront-end program on the client handles processing and presentationMore sharing of processing than file/server

DBMS/server

Client/server fundamentalsFile/server and DBMS/server are examples of client/server, in which two processes interact : the client process initiates requests and the server respondsClient/server aims to take advantage of the lower processing costs of microcomputer technologyClient is typically a desktop computer and the server is a more powerful machineProcessing is split between the client and the server, with most of the processing performed by the clientSavingsEase of use / fewer errorsLess training

Client/Server - 2nd Generation

Three-tier modelClients perform presentation functions, manage the GUI, and execute communcication software that provide network accessApplication servers the majority of the business and data logic are processed hereData servers provide support for relational and other DBMSs, also provide backup + recovery services, and transaction management control

Thick and thin clients

Type of clientThickThinTechnologyLANWebApplication logicMostly on the clientMostly on the serverNetwork loadMediumLowData storageServerServerServer intelligenceMediumHigh

Advantages of the three-tier modelSecurity is higher because logic is on the serverPerformance is betterAccess to legacy systems and a variety of databasesEasier to implement and maintain

Evolution of client/server computing

ArchitectureDescriptionTwo-tierProcessing is split between client and server, which also runs the DBMS.Three-tierClient does presentation, processing is done by the server, and the DBMS is on a separate server.N-tierClient does presentation. Processing and DBMS can be spread across multiple servers. This is a distributed resources environment.