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DATA WAREHOUSE(1)

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					DATA WAREHOUSE
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CONTENTS
 INTRODUCTION
 WHY A DATA WAREHOUSE IS REQUIRED ?
 FEATURES OF A DATA WAREHOUSE.
 DATA TRANSFORMATION IN A DATA WAREHOUSE
 HOW A DATA WAREHOUSE IS ACCESSED?
 STORAGE OF DATA IN A DATA WAREHOUSE
 TWO APPROACHES OF STORING DATA
 BENEFITS
 CONCERNS
 FUTURE ASPECTS
INTRODUCTION

 WHAT IS A DATA WAREHOUSE?
 DEFINITION ACCORDING TO INMON AND KIMBALL
       WHAT IS A DATA WAREHOUSE?
 A data warehouse is the main repository of an organization’s
  historical data and its corporate memory. It contains the raw
  material for managements decision support system. The
  critical factor leading to the use of a data warehouse is that a
  data analyst can perform complex queries and analysis such
  as data mining on the information without slowing down the
  operational systems.
      VIEWS OF INMON AND KIMBALL

  VIEW OF INMON                    VIEW OF KIMBALL
 According to Inmon the         According to Kimball, the
 data warehouse should be         warehouse should be
 designed from top-down           designed from bottom-up
 to include all the corporate     in which individual data
 data. In this methodology,       marts are created and they
 the data marts are created
                                  are later combined into a
 only after the creation of a
 complete data warehouse
                                  larger data warehouse.
WHY A DATA WAREHOUSE IS REQUIRED?
 Data warehouses were developed to meet the growing demand
  for management information and analysis that could not be met by
  the operational systems. Operational systems failed to meet the
  demand due to the following reasons:
 The processing load of reporting reduced the response time of the
  operational systems.
 The database designs of operational systems were not optimized
  for information analysis and reporting.
 Most organizations had more than one operational systems, so
  company-wide reporting could not be supported from a single
  system.
 Development of reports in operational systems often required
  writing specific computer program which was slow and expensive.
FEATURES OF DATA WAREHOUSE
 SUBJECT ORIENTED- Information is presented according to
    specific subjects or areas of interest.
   INTEGRATED-It contain data from most or all of an organizations
    operational applications.
   NON-VOLATILE- It contain stable information that doesn’t
    change whenever an operational process is executed.
   TIME-VARIENT- It contain history of subject as well as current
    information.
   ACCESSIBLE- Its primary purpose is to provide readily accessible
    information to its end users.
   PROCESS ORIENTED- Its acts as a process for delivery of
    information.
DATA TRANSFORMATION IN DATA WAREHOUSE
 EXTRACTION OF DATA- Natural algorithms are written to
  extract data.
 VERIFICATION OF DATA- Accuracy and consistency of
  data is verified.
 CREATION OF TABLES-Normalised tables are created on
  the warehouse.
 LOADING TABLES- Warehouse tables are loaded with
  extracted data.
 REFRESHING DATA- Schedule is established to refresh the
  data. Frequency depend on volatility.
                                Query Tool


                               to retrieve data




End Users                                            Data Warehouse




  HOW DATA WAREHOUSE IS ACCESSED?
  Users use query tools to get data from the data warehouse. Tools
  are off -the -self software that run on the desktop
     STORAGE OF DATA IN WAREHOUSE
 The goal of a data warehouse is to bring data together from a
  variety of existing databases to support management.
 Data is stored at its most elemental level as this provides for
  the most useful basis which is used in reporting and
  information analysis.
 Because of different focus on specific requirements there can
  be alternative methods for designing and implementing data
  warehouses.
   TWO APPROACHS TO STORE DATA

DIMENSIONAL APPROACH              NORMALIZED APPROACH
 In this approach transition      It uses database normalization
  data is partitioned into         Tables are grouped together
  measured facts which are
                                    by subject areasthat reflect
  numeric data.
                                    the general definition of data.
 The numeric data contain
  specific values or dimensions    Advantage-New information
  which contain the reference       can be added to the database.
  information for each             Disadvantage-Slow to
  transaction.                      produce information and
 Advantage-Easy for business       reports
  staff.
     BENEFITS OF DATA WAREHOUSE
 Enhance end-user access to a wide variety of data.
 Reduces cost
 Timely retrieval of data
 Flexibility
 Significant enabler of commercial business applications,
  particularly CRM systems.
       CONCERNS OF DATA WAREHOUSE
 Extracting, transforming and loading data consumes a lot
  of time.
 Data warehousing must be actively managed.
 Compatibility problems with systems exist.
 Security develop into a serious issue, especially when
  data warehouse is web accessible.
                FUTURE ASPECTS
 More data will be added to the warehouse.
 Mainframe will be primarily used for transaction
  processing.
QUESTIONS ?
THANK YOU VERY MUCH

				
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posted:9/21/2011
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Lingjuan Ma Lingjuan Ma
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