Distributed Database Systems: Fragmentation in Distributed Database Design, Slides of Distributed Database Management Systems

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In the name of Allah

Distributed Database Systems

(CS-5323)

Spring 2012

Dept of CS, MAJU, Ibd

 Schema design + schema

distribution

 Top-Down design

 Different questions about DDBSs;

why, how etc

Dept of CS, MAJU, Ibd

 Distributed DB Design concerns two major steps,

• Schema Design
• Schema Distribution

Dept of CS, MAJU, Ibd

Requirement Analysis

System Requirements (Objectives)

Conceptual Design

Global Conceptual Schema (^) Access In formation External Schema Def.

Distributed Design

Physical Design

Observation and Monitoring

View Design

Local Conceptual Schemas

Physical Schema

User Input View Integration

Feedback^ Feedback

User Input

Dept of CS, MAJU, Ibd

Bottom-Up Design Process

Dept of CS, MAJU, Ibd

 Focus now on the distribution aspect of T-D Process  Two alternatives

• Fragmentation
• Replication

Dept of CS, MAJU, Ibd

Fragmentation

Dept of CS, MAJU, Ibd

 A Fragment is a subset of a relation

that is stored on a different site from another subset of the same relation

 It gives a number of advantages

 Disadvantages:

• Difficult to manage in case of non- exclusive Fragmentation (replication)
• Maintenance of Integrity constraints

Dept of CS, MAJU, Ibd

1- Why

 But Wait

Dept of CS, MAJU, Ibd

2- How

 Unit of Fragmentation

• Entire table is not a suitable unit

Dept of CS, MAJU, Ibd

Fragmentation Alternatives

1- Vertical; Different subsets of attributes are stored at different places, like,

• Table EMP(eId, eName, eDept, eQual, eSal)
• Interests of the local and head offices may result following vertical partitions of this table: EMP1(eId, eName, eDept) EMP2(eId, eQual, eSal)

Dept of CS, MAJU, Ibd

3- Degree of Fragmentation Between no to the extreme level that could be to the individual tuple or column level; a compromised decision

Dept of CS, MAJU, Ibd

4- Correctness Rules for Fragmentation