Short Questions Answers
Q What is difference between datawarehouse and datawarehousing ?
A Datawarehouse is physical space where historical data is stored where as the process of storing this data in database is called datawarehousing.
Q What are the characteristics of datawarehouse?
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Subject- Oriented - should be related to a subject eg sales ,marketting
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Integrated- should be intehrated from various sorces after removing inconsistencies
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Non Volatile- Nonvolatile means that, once entered into the warehouse, data should not change
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Time Variant - All data in the data warehouse is identified with a particular time period.
Q What is Enterprise Data warehouse
A It collects all information about subjects (customers,products,sales,assets, personnel) that span the entire organization
Q What is Data Mart
A Departmental subsets that focus on selected subjects eg. sales data mart , hr data mart , marketting data mart etc.
Q What is Decision Support System (DSS) ?
A It is an Information technology to help the knowledge worker (executive, manager, analyst) make faster & better decisions.
Q What is difference between OLTP and datawarehouse ?
A OLTP is
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Application Oriented
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Used to run business
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Detailed data
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Current up to date
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Isolated Data
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Repetitive access
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Clerical User
Datawarehouse
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Subject Oriented
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Used to analyze business
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Summarized and refined
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Snapshot data
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Integrated Data
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Ad-hoc access
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Knowledge User (Manager)
Q What is difference between ROLAP, MOLAP and HOLAP ?
A Relational OLAP (ROLAP)
–Relational and specialized relational DBMS to store and manage warehouse data
–OLAP middleware to support missing pieces
Multidimensional OLAP (MOLAP)
–Array-based storage structures
–Direct access to array data structures
Hybrid OLAP (HOLAP)
–Storing detailed data in RDBMS
–Storing aggregated data in MDBMS
–User access via MOLAP tools