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Lecture 08 distributed dbms

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  • Product table should be Customer table and Customer table as Product table mistake in this slide
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    • 1. Lecture 8 Distributed Database Management Systems
    • 2. Different Types of Database System Contributed by: Isha Kushwah MCA-2008-11 Centralized database System
    • 3. Content
      • What a distributed database management system (DDBMS)
      • DDBMS components
      • Database implementation is affected by different levels of data and process distribution
      • How transactions are managed in a distributed database environment
      • How database design is affected by the distributed database environment
    • 4. Evolution of DDBMS
      • Decentralized database management systems (DDBMS)
        • Interconnected computer systems
        • Data/processing functions reside on multiple sites
      • 1970’s: Centralized DBMS
      • 1980’s: Social and Technical Changes
        • Ad hoc capability required
        • Decentralized management structure common
      • 1990’s: New forces
        • Internet and the World Wide Web used for data access and distribution
        • Data analysis through data mining and data warehousing
    • 5. Problem in Centralized database Management
      • Performance degradation
      • High cost
      • Reliability problems
    • 6. DDBMS Advantages
      • Data located near site with greatest demand
      • Faster data access
      • Faster data processing
      • Growth facilitation
      • Improved communications
      • Reduced operating costs
      • User-friendly interface
      • Less danger of single-point failure
      • Processor independence
    • 7. DDBMS Disadvantages
      • Complexity of management and control
      • Security
      • Lack of standards
      • Increased storage requirements
      • Greater difficulty in managing data environment
      • Increased training costs
    • 8. Distributed Processing
      • Shares database’s logical processing among physically, networked independent sites
      Figure 10.1
    • 9. Distributed Database
      • Stores logically related database over physically independent sites
      Figure 10.2
    • 10. Distributed Database vs. Distributed Processing
      • Distributed processing
        • Does not require distributed database
        • May be based on a single database on single computer
        • Copies or parts of database processing functions must be distributed to all data storage sites
      • Distributed database
        • Requires distributed processing
      • Both
        • Require a network to connect components
    • 11. Functions of DDBMS
      • Application/end user interface
      • Validation
      • Transformation
      • Query optimization
      • Mapping
      • I/O interface
      • Formatting
      • Security
      • Backup and recovery
      • DB Administration
      • Concurrency Control
      • Transaction Management
    • 12. Functions of DDBMS
      • Application/end user interface
      • Validation to analyze data requests
      • Transformation to determine request components
      • Query optimization to find the best access strategy
      • Mapping to determine the data location
      • I/O interface to read or write data
      • Formatting to prepare the data for presentation
      • Security to provide data privacy
      • Backup and recovery
      • DB Administration
      • Concurrency Control
      • Transaction Management
    • 13. Centralized Database Figure 10.3
    • 14. Fully Distributed Database Management System Figure 10.4
    • 15. DDBMS Components
      • Computer workstations
      • Network hardware and software components
      • Communications media
      • Transaction processor (TP)
        • Also called application manager (AP) or transaction manager (TM)
      • Data processor (DP)
        • Also called data manager (DM)
    • 16. Distributed Database Components Figure 10.5
    • 17. DDBMS Protocols
      • Interface with network to transport data and commands between DPs and TPs
      • Synchronize data received from DPs and route to appropriate TPs
      • Ensure common database functions
        • Security
        • Concurrency control
        • Backup and recovery
    • 18. Levels of Data and Process Distribution
      • Database systems can be classified based on process distribution and data distribution
      Table 10.1
    • 19. Single-Site Processing, Single-Site Data (SPSD)
      • All processing on single CPU or host computer
      • All data are stored on host computer disk
      • DBMS located on the host computer
      • DBMS accessed by dumb terminals
      • Typical of mainframe and minicomputer DBMSs
      • Typical of 1st generation of single-user microcomputer database
    • 20. Single-Site Processing, Single-Site Data (con’t.) Figure 10.6
    • 21. Multiple-Site Processing, Single-Site Data (MPSD)
        • Requires network file server
        • Applications accessed through LAN
        • Variation known as client/server architecture
      Figure 10.7
    • 22. Multiple-Site Processing, Multiple-Site Data (MPMD)
      • Fully distributed DDBMS with support for multiple DPs and TPs at multiple sites
        • Homogeneous I
          • Integrate one type of centralized DBMS over the network
        • Heterogeneous
          • Integrate different types of centralized DBMSs over a network
    • 23. Heterogeneous Distributed Database Scenario Figure 10.8
    • 24. Distributed DB Transparency
      • Allows end users to feel like only database user
      • Hides complexities of distributed database
      • Transparency features
        • Distribution
        • Transaction
        • Failure
        • Performance
        • Heterogeneity
    • 25. Distribution Transparency
      • Allows management of a physically dispersed database as though it were centralized
      • Three Levels
        • Fragmentation transparency
        • Location transparency
        • Local mapping transparency
      Table 10.2
    • 26. Transaction Transparency
      • Ensures transactions maintain integrity and consistency
      • Completed only if all involved database sites complete their part of the transaction
      • Management mechanisms
        • Remote request
        • Remote transaction
        • Distributed transaction
        • Distributed request
    • 27. Remote Request Figure 10.10
    • 28. Remote Transaction Figure 10.11
    • 29. Distributed Transaction Figure 10.12
    • 30. Distributed Requests Figure 10.13
    • 31. Distributed Requests (con’t.) Figure 10.14
    • 32. Distributed Concurrency Control
      • Multisite, multiple-process operations more likely to create data inconsistencies and deadlocked transactions
      • Problems
        • Transaction committed by local DP
        • One DP could not commit transaction’s result
        • Yields inconsistent database
    • 33. Two-Phase Commit Protocol
      • DO-UNDO-REDO protocol
        • Write-ahead protocol
        • Two kinds of nodes
          • Coordinator
          • Subordinates
      • Phases
        • Preparation
          • Coordinator sends message to all subordinates
          • Confirms all are ready to commit or abort
        • Final Commit
          • Ensures all subordinates have committed or aborted
    • 34. Performance Transparency and Query Optimization
      • Objective: Minimize total cost associated with execution of request
      • Main costs
        • Access time
        • Communication
        • CPU time
      • Basis for query optimization algorithms
        • Optimum execution order
        • Sites accessed to minimize communication costs
      • Automatic or Manual
      • Dynamic or static optimization
      • Statistically based vs. rule-based query optimization algorithms
    • 35. Distributed Database Design
      • Partition database into fragments
        • Horizontal
        • Vertical
        • Mixed
      • Fragments to replicate
        • Storage of data copies at multiple sites
        • Fully, partially, unreplicated databases
      • Data allocation
        • Where to locate data
        • Centralized, partitioned, replicated
    • 36. Client/Server Advantages Over DDBMS
      • Client/server less expensive
      • Client/server solutions allow use of microcomputer’s GUI
      • More people with PC skills than mainframe skills
      • PC is well established in workplace
      • Numerous data analysis and query tools exist
      • Considerable cost advantages to off-loading application development
    • 37. Client/Server Disadvantages
      • Creates more complex environment with different platforms
      • Increased number of users and sites creates security problems
      • Training issues become more complex and expensive
    • 38. Date’s 12 Commandments for Distributed Databases
      • 1 . Local Site Independence
      • 2. Central Site Independence
      • 3. Failure Independence
      • 4. Location Transparency
      • 5. Fragmentation Transparency
      • 6. Replication Transparency
    • 39. Date’s 12 Commandments for Distributed Databases
      • 7. Distributed Query Processing
      • 8. Distributed Transaction Processing
      • 9. Hardware Independence
      • 10. Operating System Independence
      • 11. Network Independence
      • 12. Database Independence