march 24, 2004craig e. ward, cmsi 698 advanced topics in database systems database architecture...

March 24, 2004 Craig E. Ward, CMSI 698 Advanced Topics in Database Systems

Database Architecture Database Architecture OverviewOverview

Database Architecture Database Architecture OverviewOverview

Client-Server and Distributed Client-Server and Distributed ArchitecturesArchitectures


Agenda• Traditional Client-Server Architecture

• 3-Tier Client-Server and the WWW

• Distributed Database Architecture

• Changes since the 1997 Kramer paper


Client-Server Architecture


Spreading the Server Responsibilities


Benefits of n-tier Architectures

• Allows for cleaner separation of– Presentation (user interface)– Business logic– Database server

• But where are the lines to be drawn?


Implementations on the WWW

• Web browser as client– HTML, JavaScript for lightweight– Java Applets for heavyweight

• Web server as application server– Dynamic content from CGI, Java servlets, JSP,

ASP

• Database engine in the background– Oracle, MySQL, SQL Server


Why Distributed Database Systems?

• Transparency

• Reliability and Availability

• Performance

• Expandability


Transparency• Distribution or network transparency

– location– naming

• Replication transparency• Fragmentation transparency

– horizontal– vertical


Reliability and Availability• Reliability is the probability that a

system will be running at some particular time.

• Availability is the probability that a system will be running and usable over a time interval.


Performance• Remote data that feels local


Expandability• Easier to grow something that is

already spread around.


Horizontal Fragmentation• Derived Horizontal Fragmentation

– Split whole relations


Vertical Fragmentation• Splitting the attributes between

fragments, duplicating the primary key to allow full reconstruction of the tuple.


Additional DDBMS Issues• Keeping track of where data is• Distributed query processing• Distributed transaction management• Management of data replication• New problems for recovery• Security• Distributed directory management


Types of Distributed Database Systems

• Homogeneous

• Heterogeneous

• Federated databases

• Multi-database


Since 1997• Java to the backend server

• CORBA alternatives

• Applets replaced by server-side dynamic processing

• CGI no longer in favor


Diagram


Questions and Discussion

march 24, 2004craig e. ward, cmsi 698 advanced topics in database systems database architecture...

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