Data sources often store only current data, not historical data

Corporate decision making requires a unified view of all organizational data, including historical data

2

Data warehouse A physical repository where relational data are

specially organized to provide enterprise-wide, cleansed data in a standardized format

A DW delivers a collection of integrated data used to support the decision making process for the enterprise

3

A data warehouse is a repository (archive) of information gathered from multiple sources, stored under a unified schema, at a single site

Greatly simplifies querying, permits study of historical trends

Shifts decision support query load away from transaction processing systems

4

5

Characteristics of data warehousing Subject oriented ▪ organized based on use: sales, products, customers

6

Characteristics of data warehousing Integrated ▪ inconsistencies removed

7

Characteristics of data warehousing Time variant: data are normally time series, A

warehouse maintains historical data

Nonvolatile: stored in read-only format, periodically refreshed, Changes are recorded as new data

8

Characteristics of data warehousing Summarized ▪ in decision-usable format

Large volume ▪ data sets are quite large

Non normalized ▪ often redundant

Metadata ▪ data about data are stored

9

Integrated, company-wide view of high-quality information (from disparate databases)

Separation of operational and informational systems and data (for improved performance)

10

Data mart A departmental data warehouse that stores

only relevant data Focuses on a particular subject or department

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Organizational

Data

Warehouse

Finance

Data Mart

Accountin

g

Data Mart

Marketing

Data Mart

Sales

Data Mart

Operational

Data Store

Operational

Data Store

Operational

Data Store

Operational

Data Store

Legacy

Systems

Legacy

systems

feed data to

the

warehouse.

The

warehouse

feeds

specialized

information to

departments. 12

Organizational

Data

Warehouse

Finance

Data Mart

Accting

Data Mart

Marketing

Data Mart

Sales

Data Mart

Data Marts

Departmentalized

Summarized, aggregated

data

Star join design

Limited historical data

Limited data volume

Requirements driven data

Focused on departmental

needs

Multi-dimensional DBMS

technologies

Organizational Data

Warehouse

Corporate

Highly granular data

Normalized design

Robust historical data

Large data volume

Data Model driven data

Versatile

General purpose DBMS

technologies

The data

mart serves

the needs of

one

business

unit, not the

organization.

13

Dependent data mart A subset that is created directly from a data

warehouse Quality data

Support enterprise wide data model

14

Independent data mart A small data warehouse designed for a

strategic business unit or a department, but its source is not an EDW

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Operational data stores (ODS) A type of database often used as an interim

area for a data warehouse, especially for customer information files

Volatile Used for short-term decisions involving

mission-critical application

Store only very recent information

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Oper marts An operational data mart. An oper mart is a

small-scale data mart typically used by a single department or functional area in an organization

The data for an oper-mart come from an ODS

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Enterprise data warehouse (EDW)

Is a large scale DW that is used across the enterprise for decision support

A technology that provides a vehicle for pushing data from source systems into a data warehouse

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Metadata Data about data. In a data warehouse,

metadata describe the contents of a data warehouse and the manner of its use

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Metadata

As with other databases, a warehouse must include a metadata repository

▪ Information about physical and logical organization of data

▪ Information about the source of each data item and the dates on which it was loaded and refreshed

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Direct benefits of a data warehouse

Allows end users to perform extensive analysis

Allows a consolidated view of corporate data

Better and more timely information

Enhanced system performance

Simplification of data access

Data integration

No more redundancy

Consistency of data content

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Direct benefits of a data warehouse

Improved data quality

Historical enterprise data

Unlimited, ad-hoc reporting

Reliable trend analysis reporting

Faster data delivery and data access

Business intelligence (BI) capabilities

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Indirect benefits result from end users using these direct benefits

Enhance business knowledge

Present competitive advantage

Enhance customer service and satisfaction

Facilitate decision making

Help in reforming business processes

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DECISION SUPPORT SYSTEMS AND BUSINESS INTELLIGENCE. Turban

Modern Data Warehousing, Mining, and Visualization: Core Concepts. George M. Marakas

Modern Database Management.9th Edition.Jeffrey A. Hoffer, Mary B. Prescott, Heikki Topi

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