Light sayed database_system_architecture

Light sayed database_system_architecture

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  DATABASE SYSTEM ARCHITECTURE SayedAhmed Computer Engineering, BUET, Bangladesh MSc, Computer Science, U of Manitoba, Canada Owner/President/Architect/Developer Justetc (Just et cetera) Technologies http://www.justetc.net http://sayed.justetc.net sayed@justetc.net
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  FREE TRAINING BYJUSTETC  Training and Education in Bangla:  http://Bangla.SaLearningSchool.com  http://Blog. SaLearningSchool.com  Training and Education in English:  http://www.SaLearningSchool.com  http://English.SaLearningSchool.com  http://www.SitesTree.com ---------------------------------------------------------------------------------  Ask questions and get answers  http://Ask.JustEtc.net ---------------------------------------------------------------------------------  Offline IT Training:  http://University.JustEtc.net
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  LEARNING OBJECTIVES  Understanddifferent database system architectures  Comparison of different database system architectures  Note:  Bangladesh Polytechnique Institute  Subject Code: 6658, will be helpful  Grade 9 to 12 (Bangladesh) students may be benefited
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  DATABASE SYSTEM ARCHITECTURES DBMS architecture depends on the Computer System Architecture  DBMS architecture types  Centralized Systems  Client--Server Systems  Parallel Systems  Distributed Systems
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  CENTRALIZED SYSTEMS  TheDBMS resides, Run, and sits on a single computer system  The DBMS does not interact with other computer systems  Can be called One Tier Architectures  Microsoft Access  Mainframe computer databases  Reference:  http://www.windowsecurity.com/whitepapers/softwar e_engineering/An-Overview-of-Common-Database- Architectures.html
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  A CENTRALIZED COMPUTERSYSTEM
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  CLIENT-SERVER SYSTEMS  Client-servercomputer systems  Server systems satisfy requests generated at m client systems as shown in the image below  DBMS located in the server also respond to the clients similar way
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  CLIENT-SERVER SYSTEMS (CONT.) Database functionality can be divided into:  Back-end: manages access structures, query evaluation and optimization, concurrency control and recovery.  Front-end: consists of tools such as forms, report-writers, and graphical user interface facilities.  The interface between the front-end and the back-end is through SQL or through an application program interface.
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  CLIENT-SERVER SYSTEMS (CONT.) Examples  MS SQL Server, Oracle, Sybase in general  Can be of Thin Client and Fat-Client type  Server systems can be broadly categorized into two kinds:  transaction servers (thin-client)  widely used in relational database systems  data servers (usually fat-client),  used in object-oriented database systems
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  TRANSACTION SERVERS  Alsocalled query server systems or SQL server systems;  clients send requests to the server system where the transactions are executed, and results are shipped back to the client.
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  TRANSACTION SERVER PROCESSSTRUCTURE  Transaction Server Processes  Server processes  Lock manager process  Database writer process  Log writer process  Checkpoint process  Process monitor process
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  DATA SERVERS  Usedin LANs, where  there is a very high speed connection between the clients and the server  the client machines are comparable in processing power to the server machine  the tasks are compute intensive  Ship data to client machines where processing is performed  And then ship results back to the server machine.  This architecture requires full back-end functionality at the clients.  Used in many object-oriented database systems  Issues:  Page-Shipping versus Item-Shipping  Locking  Data Caching  Lock Caching
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  PARALLEL SYSTEMS  Onesingle DBMS in a parallel computer  The same DBMS can be accessed by the processors and can span over multiple hard drives if any in that computer  Parallel database systems consist of multiple processors and multiple disks connected by a fast interconnection network.  A coarse-grain parallel machine  consists of a small number of powerful processors  A massively parallel or fine grain parallel  machine utilizes thousands of smaller processors.  Two main performance measures:  throughput --- the number of tasks that can be completed in a given time interval  response time --- the amount of time it takes to complete a single task from the time it is submitted
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  PARALLEL DATABASE ARCHITECTURES Shared memory  processors share a common memory  Shared disk  processors share a common disk  Shared nothing  processors share neither a common memory nor common disk  Hierarchical  hybrid of the above architectures
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  PARALLEL DATABASE ARCHITECTURES
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  DISTRIBUTED SYSTEMS  Dataspread over multiple machines (also referred to as sites or nodes.  Network interconnects the machines  Data shared by users on multiple machines
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  DISTRIBUTED DATABASES  Homogeneousdistributed databases  Same software/schema on all sites, data may be partitioned among sites  Goal: provide a view of a single database, hiding details of distribution  Heterogeneous distributed databases  Different software/schema on different sites  Goal: integrate existing databases to provide useful functionality  Differentiate between local and global transactions  A local transaction accesses data in the single site at which the transaction was initiated.  A global transaction either accesses data in a site different from the one at which the transaction was initiated or accesses data in several different sites.
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  TRADE-OFFS IN DISTRIBUTEDSYSTEMS  Sharing data  users at one site able to access the data residing at some other sites.  Autonomy  each site is able to retain a degree of control over data stored locally.  Higher system availability through redundancy  data can be replicated at remote sites, and system can function even if a site fails.  Disadvantage: added complexity required to ensure proper coordination among sites.  Software development cost  Greater potential for bugs  Increased processing overhead
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