What is Data Warehousing ?

• The word "Data Warehousing" coined by Bill Inmon in 1990.
• Data Warehousing is the collection of Electronically Stored Data of An Organization.
• Which has the Subject Oriented,Time Variant, Integrity and Non-Volatile.
• The stored data in Data Warehousing is used for Business Decisions and For Generating The Reports.
• Data Warehousing is the collection of large amount of data in DWH.
• DWH is the storage Area which is used to store the Historical data which is used to Business Decisions by Management, Executives and Analysts.
• DWH stores current data and Historical data. The historical Data used for Generating the Reports, Using in Data Mining and Analytics,
• It is an OLAP System(Online Analytical Process).
• DWH is based on Star Schema and SnowFake Schema.
• The Database Size is 100GB to 100TB
• DWH are Highly Flexible. 
• But here the Number of users are very less compare  to Operational Database(OLTP) Systems.
• It Provides the summarized Data .
• In DWH data used for READ ONLY purpose not for modifications.