Prepared By :
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
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
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
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
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
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
ACCESSIBLE- Its primary purpose is to provide readily accessible
information to its end users.
PROCESS ORIENTED- Its acts as a process for delivery of
DATA TRANSFORMATION IN DATA WAREHOUSE
EXTRACTION OF DATA- Natural algorithms are written to
VERIFICATION OF DATA- Accuracy and consistency of
data is verified.
CREATION OF TABLES-Normalised tables are created on
LOADING TABLES- Warehouse tables are loaded with
REFRESHING DATA- Schedule is established to refresh the
data. Frequency depend on volatility.
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
Because of different focus on specific requirements there can
be alternative methods for designing and implementing data
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
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
BENEFITS OF DATA WAREHOUSE
Enhance end-user access to a wide variety of data.
Timely retrieval of data
Significant enabler of commercial business applications,
particularly CRM systems.
CONCERNS OF DATA WAREHOUSE
Extracting, transforming and loading data consumes a lot
Data warehousing must be actively managed.
Compatibility problems with systems exist.
Security develop into a serious issue, especially when
data warehouse is web accessible.
More data will be added to the warehouse.
Mainframe will be primarily used for transaction
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