csce824-lecture5

csce824-lecture5 - Distributed Database Distributed...

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Unformatted text preview: Distributed Database Distributed Database Management Systems Reading Reading Farkas Textbook: Ch. 1, Ch. 3 For next class: Ch. 4 CSCE 824 ­ Spring 2011 2 Database Management System (DBMS) Collection of – interrelated data and – set of programs to access the data Convenient and efficient processing of data Database Application Software Farkas Farkas CSCE 824 ­ Spring 2011 3 Abstraction View level: different perspectives – application programs hide irrelevant data Logical level: data models – Logical representation of data – Different approaches: relational, hierarchical, network, object oriented, semi­structured, etc. – Data independence principle Farkas Farkas Physical level: how data is stored CSCE 824 ­ Spring 2011 4 Motivation for DBMS Motivation for DBMS Farkas Integrate related data Provide centralized and controlled access to data CSCE 824 ­ Spring 2011 5 Computer Network Computer Network Distributed processing: – Number of autonomous processing elements that are interconnected by computer network – Cooperate to perform their assigned tasks Farkas CSCE 824 ­ Spring 2011 6 What to distribute? What to distribute? Farkas Processing logic/element Functions Data Control of execution CSCE 824 ­ Spring 2011 7 Why to distribute? Why to distribute? Farkas Intuition Reliability Performance CSCE 824 ­ Spring 2011 8 Distributed Database Distributed Database Systems Distributed database: – Collection of multiple, logically interrelated databases that are distributed over a computer network Distributed DBMS: software system that – Permits the management of the distributed database and – Makes the distribution transparent to the user Farkas CSCE 824 ­ Spring 2011 9 Data Delivery Data Delivery Data storage and query processing Data delivery: Delivery mode: push, pull, hybrid Frequency: periodic, conditional, ad­hoc, irregular – Communication method: unicast, one­to­ many – – Farkas CSCE 824 ­ Spring 2011 10 DDBMS Services DDBMS Services Transparent data management – Distributed, replicated data – Transparency: network, replica, fragmentation Reliable access to data – Distributed transactions – Failure atomicity Improved performance Flexible expansion Farkas CSCE 824 ­ Spring 2011 11 Difficulties Difficulties Everything that is present in traditional DBs Fragmentation and replica control – Data retrieval – Data update Farkas Dealing with failures Synchronization CSCE 824 ­ Spring 2011 12 DDBMS Issues DDBMS Issues Farkas Database design Directory management Query processing Concurrency control Deadlock management Reliability Replication CSCE 824 ­ Spring 2011 13 DDBMS Architecture DDBMS Architecture Chapter 1.7 (read only) – Client/server – P2P – Multi­database Farkas CSCE 824 ­ Spring 2011 14 DISTRIBUTED DATABASE DISTRIBUTED DATABASE DESIGN Farkas CSCE 824 ­ Spring 2011 15 Design Issues Design Issues Farkas Placing of data and programs (DBMS and application) Network issues CSCE 824 ­ Spring 2011 16 Level of Sharing Level of Sharing No sharing Data sharing Data and program sharing Heterogeneous environment! Farkas CSCE 824 ­ Spring 2011 17 Access Pattern Access Pattern Farkas Static Dynamic CSCE 824 ­ Spring 2011 18 Level of Knowledge on Level of Knowledge on Access Behavior Farkas Complete information Partial information CSCE 824 ­ Spring 2011 19 Top­Down Design Top­Down Design Farkas Figure 3.2 CSCE 824 ­ Spring 2011 20 Fragmentation Fragmentation Why to fragment the data? – Application views – Limit replication while increase availability – Increased concurrency Farkas CSCE 824 ­ Spring 2011 21 Fragmentation Fragmentation Types: – Horizontal – Vertical – Hybrid Degree: – From no fragmentation to individual tuples/attributes Farkas CSCE 824 ­ Spring 2011 22 Correctness of Correctness of Fragmentation 1. Completeness: FR={R1, …, Rn} 2. Reconstruction: R=∇ Ri, ∀Ri∈R 1&2: Lossless­join (normalization) 3. Disjointness: – – Farkas Horizontal: does not ∃ dj∈Ri such that dj∈Rk where k≠ i Vertical: same as horizontal for non­primary key attributes CSCE 824 ­ Spring 2011 23 Allocation Allocation Replication or single copy? – Read­only transactions Issues: (Figure 3.6) – – – – Query processing Directory management Concurrency control Reliability Real world applications Farkas CSCE 824 ­ Spring 2011 24 Fragmentation Design Fragmentation Design Information need: – – – – Farkas Database information Application information Communication network information Computer system information CSCE 824 ­ Spring 2011 25 Horizontal Fragmentation Horizontal Fragmentation Primary horizontal fragmentation: defined by selection operation on the relations of a database schema, Ri= σFi(R) Correctness: Farkas – Completeness – Reconstruction (union) – Disjointness CSCE 824 ­ Spring 2011 26 Vertical Fragmentation Vertical Fragmentation R={R1, …, Rn}, where each Ri (i=1, …, n) contains a primary key and some of the attributes in R More difficult than horizontal fragmentation – heuristics – Grouping – Splitting Farkas CSCE 824 ­ Spring 2011 27 Vertical Fragmentation Vertical Fragmentation Correctness: – Completeness – Reconstruction (join) – Disjointness Farkas CSCE 824 ­ Spring 2011 28 Hybrid Fragmentation Hybrid Fragmentation Farkas Horizontal or vertical fragmentations are not sufficient the user application requirements Nested or mixed fragmentation CSCE 824 ­ Spring 2011 29 Data Directory Data Directory Global vs. local conceptual schemas – How to search? – Where to store? – Single vs. multiple copies? Farkas CSCE 824 ­ Spring 2011 30 Current Research Current Research Farkas Allocation: new requirements, technology, etc. Where to store the fragments? Dynamic environment – – – – Usage pattern Application characteristics Network changes Security CSCE 824 ­ Spring 2011 31 Next Class Database Integration Chapter 4 Farkas Farkas CSCE 824 ­ Spring 2011 32 Project Information Project Information Farkas http://www.cse.sc.edu/~farkas/csce824­2011/ CSCE 824 ­ Spring 2011 33 ...
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This note was uploaded on 12/13/2011 for the course CSCE 824 taught by Professor Staff during the Fall '11 term at South Carolina.

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