A Data Warehouse is a subject-oriented integrated time-varying non-volatile COLLECTION OF DATA THAT is used PRIMARILY IN ORGANIZATIONAL DECISION MAKING. - Bill Inmon,Building the Data Warehouse 1996 A process of transforming data into information and making it available to users in a timely enough manner to make a difference Forrester Research April 1996 Data Warehouse Architecture OLTP vs Data Warehouse OLTP Data Warehouse Application Oriented Used to Run Business Detailed Data Current Up to Date Isolated Data Repetitive Access User Specific Performance Sensitive Less Records accessed at a time Read/Update Access No Data Redundancy (Normalization) Subject Oriented Used to Analyze Business Summarized and Refined Snapshot Data Integrated Data Ad-hoc Access Business User Performance Relaxed Large Volumes at a time Mostly Read(Batch Update) Redundancy Present (De normalized) ETL (Extraction ,Transformation and Loading) is a process by which d
