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ICS 434 Advanced Database Systems

Explore the classification and components of client-server architectures in advanced database systems, emphasizing benefits, components, and architecture types. Understand the advantages of the three-tier architecture model.

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ICS 434 Advanced Database Systems

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  1. ICS 434Advanced Database Systems Dr. Abdallah Al-Sukairi sukairi@kfupm.edu.sa Second Semester 2003 - 2004 (032) King Fahd University of Petroleum & Minerals Information & Computer Science Department

  2. Outline • The Relational Data Model: Version 2 • Advanced Data Modeling • Client-Server Architecture • Client-Server Databases & Tools • Databases on the Web • The System Catalog • Query Processing and Optimization • Transaction Processing • Concurrency Control • Recovery • Administration & Security • Distributed Databases • Database Replication • Object-Oriented Databases • Data Warehousing and Data Mining • Other Emerging Database Technologies

  3. 3. Client-Server Architecture

  4. Classification of DBMSs • Mainframe (host-based) DBMSs • PC-Based DBMSs • Single user • File/Server • Client-Server Database Systems • Distributed DBMSs

  5. Mainframe (Host-Based) DBMSs • Multi-user environment • Information sharing • Centralized data management • Sophisticated administration and security features • Advanced operating system features

  6. PC-Based DBMSs • Graphical User Interface (GUI) • Ease of use • Outstanding price/performance ratio • Advanced communication • Individual environment • Increasingly powerful hardware and software • RISC-based workstations • Multiprocessing systems

  7. File/Server • Multi-User (LAN version) File Server PC PC PC PC PC

  8. Client-Server Database Systems Server Shared Database Client Server DBMS Appl. Soft. Comm. Soft. Comm. Soft. Comm. Soft. Comm. Soft. Appl. Soft. Appl. Soft.

  9. File/server vs. Client-Server User station • Server select students with GPA > 3.0 The whole table students with GPA > 3.0 only

  10. Why Client-Server ? • Mainframe Computing • Desktop Computing • Client-Server computing combines the benefits of both worlds • Downsizing trend • Scalability • Openness • Enterprise-wide computing model

  11. … Why Client-Server ? • A form of distributed processing • Hardware • LAN • Back-end Server • Front-end station • Software • Communication software • Back-end software • Front-end tool • Applications • Client-Server Databases • E-mail software • GroupWare

  12. Client-Server Database Model SQL Protocol Front-End Application Back-End Database Engine Network Protocol Network Software Network Software Network Hardware Network Hardware Physical Link User Station SQL Server Station

  13. Components of Data-Intensive Systems • Three separate types of functionality: • Data management • Application logic • Presentation • The system architecture determines whether these three components reside on a single system (“tier) or are distributed across several tiers

  14. Single-Tier Architectures • All functionality combined into a single tier, usually on a mainframe • User access through dumb terminals • Advantages: • Easy maintenance and administration • Disadvantages: • Today, users expect graphical user interfaces. • Centralized computation of all of them is too much for a central system

  15. Client-Server Architectures • Work division: Thin client • Client implements only the graphical user interface • Server implements business logic and data management • Work division: Thick client • Client implements both the graphical user interface and the business logic • Server implements data management

  16. Two-Tier Client/Server Architecture

  17. Components of Client/Server Architecture • Client • Front-end application • Server • Back-end application • Communications middleware • Communications layer

  18. … Client-Server Architectures • Disadvantages of thick clients • No central place to update the business logic • Security issues: Server needs to trust clients • Access control and authentication needs to be managed at the server • Clients need to leave server database in consistent state • One possibility: Encapsulate all database access into stored procedures • Does not scale to more than several 100s of clients • Large data transfer between server and client • More than one server creates a problem: x clients, y servers: x*y connections

  19. The Three Layers • Presentation tier • Primary interface to the user • Needs to adapt to different display devices (PC, PDA, cell phone, voice access?) • Middle tier • Implements business logic (implements complex actions, maintains state between different steps of a workflow) • Accesses different data management systems • Data management tier • One or more standard database management systems

  20. The Three-Tier Architecture Client Program (Web Browser) Presentation tier Application Server Middle tier Database System Data managementtier

  21. Three-Tier Client/Server Architecture

  22. Advantages of the Three-Tier Architecture • Heterogeneous systems • Tiers can be independently maintained, modified, and replaced • Thin clients • Only presentation layer at clients (web browsers) • Integrated data access • Several database systems can be handled transparently at the middle tier • Central management of connections • Scalability • Replication at middle tier permits scalability of business logic • Software development • Code for business logic is centralized • Interaction between tiers through well-defined APIs: Can reuse standard components at each tier

  23. Example 1: Airline reservations • Build a system for making airline reservations • What is done in the different tiers? • Database System • Airline info, available seats, customer info, etc. • Application Server • Logic to make reservations, cancel reservations, add new airlines, etc. • Client Program • Log in different users, display forms and human-readable output

  24. Example 2: Course Enrollment • Build a system using which students can enroll in courses • Database System • Student info, course info, instructor info, course availability, pre-requisites, etc. • Application Server • Logic to add a course, drop a course, create a new course, etc. • Client Program • Log in different users (students, staff, faculty), display forms and human-readable output

  25. Client/Server DBMS Functions • Transparent data access to multiple, heterogeneous clients • Allow client requests to the database server over network • Process client data requests at local server • Send only SQL results to clients over network

  26. Summary: Advantages of Client/Server Systems • Lower network traffic • Improved processing distribution • Thinner clients • Greater processing transparency • Increased network, hardware, and software transparency • Improved security • Decreased costs • Increased scalability

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