An overview of data warehousing and olap technology
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An overview of Data Warehousing and OLAP Technology. Presented By Manish Desai. Introduction What is data warehouse ? Explanation of definition Data warehouse Vs. Operational Database Data warehouse architecture Back end tools Conceptual model Database design Warehouse servers

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Presentation Transcript

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  • Introduction

  • What is data warehouse ?

  • Explanation of definition

  • Data warehouse Vs. Operational Database

  • Data warehouse architecture

  • Back end tools

  • Conceptual model

  • Database design

  • Warehouse servers

  • Index structures

  • Meta data

  • Conclusion

  • References

Introduction l.jpg

  • Essential elements of decision support

  • Enables The Knowledge Worker to make better and faster decisions

  • Used in many industries like:

    • Manufacturing (for order shipment)

    • Retail (for inventory management)

    • Financial Services (claims and risk analysis)

  • Every major database vendor offers product in this area

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What is Data Warehouse ?

  • A data warehouse is a “subject-oriented, integrated, time-varying, non-volatile collection of data that is used primarily in organizational decision making”

  • Typically maintained separately from operational databases

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Explanation of definition

  • Subject-Oriented:

    • Designed around subject such as customer, vendor, product and activity

    • Does not includes data that are not needed for Decision support system (DSS)

  • Integrated:

    • Most important feature

    • Consistent naming convention, measurement of variables and so forth

    • The data should be stored in single globally acceptable fashion

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Explanation (continues…)

  • Time Varying:

    • All data in the warehouse should be accurate as of some moment in time

    • Data stored over a long time horizon (5 –10 years)

    • Key structure contains element of time (implicitly or explicitly)

    • Data once correctly recorded cant be updated

  • Non Volatile:

    • No Update of data allowed

    • only loading and access of data operations

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  • Data sourcing,migration,cleanup tools

  • Meta data repository

  • Data marts

  • Data query, reporting, analysis and mining tools

  • Data warehouse administration and management

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Architecture (continues…)

  • Distributed Data warehouse

    • Load balancing, scalability,higher availability

    • Meta data replicated and centrally administrated

    • Too expansive

  • Data marts

    • Departmental subset focused on selected subjects

    • example: marketing department includes customer, sales and product tabels

    • Has own repository and administration

    • May lead to complex integration problems if not designed properly

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Back end tools and Utilities

  • Data cleaning, loading, refreshing tools

  • Cleaning

    • Multiple source, possibility of errors

    • Example: replace string sex by gender

  • Loading

    • Building indices, sorting and making access paths

    • Large amount of data

      • Incremental loading

      • Only updated tuples are inserted ,Process hard to manage

  • Refresh

    • Propagating updates

    • When to refresh ?

    • Set by administrator depending on user needs and traffic

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Conceptual Model and front end tools

  • Multi dimensional view

    • Dimensions together uniquely determine the measure

    • Example: Sales can be represented as city,product, data

    • Each dimension is described by set of attribute

    • Example: product consist of

      • Category of product

      • Industry of product

      • Year of introduction

  • Front end tools

    • Multi dimensional spreadsheet

      • Supports Pivoting-reorientation

      • Roll_up - summarized data

      • Drill_down - go from high level to low level summary

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Database design

  • Two ways to represent Multi dimensional model

    • Star schema

      • Database consist of single fact table and single table for each dimension

      • Each tuples in fact table consist of pointer to each of dimension

    • Snowflake schema

      • Refinement over star schema

      • Dimensional hierarchy is explicitly represented by normalizing dimension tables

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Warehouse Servers

  • Specialized SQL servers

    • Provides advanced query language and query processing support for SQL queries over star and snowflake schemas

    • Example: Redbrick


    • Between relational back end and client front end tools

    • Extend traditional relational servers to support multidimensional queries

    • Example: Microstratergy


    • Multidimensional storage engine

    • Direct mapping

    • Example: Essbase from Arbor Inc.

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Index structures

  • Bit map indices

    • Use single bit to indicate specific value of attribute

    • Example:

      instead of storing eight characters to record “engineer” as skill of employee use single bit

      id# Name Skill

      1000 John 1

  • Join indices

    • Maintains the relationship between foreign key with its matching primary keys

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Meta data and warehouse management

  • Its data about data

  • Used for building, maintain, managing and using data warehouse

  • Administrative meta data

    • Information about setting up and using warehouse

  • Business meta data

    • Business terms and definition

  • Operational meta data

    • Information collected during operation of warehouse

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  • Data warehouse is the technology for the future.

  • data warehouse enables knowledge worker to make faster and better decisions

References l.jpg

  • Inmon W. H.,Building the data warehouse




  • Kimball, R. The data warehouse toolkit.