Tuesday, 22 March 2016

Data Warehouse


Data Warehousing :-
DWH (Data Warehousing)  is type of relational data base system specially designed for query analysis processing rather than transactional processing.
1. The DWH systems are also called as Historical Db’s, Read only Db’s, Integrated Db’s, Decision Supporting System, Executive info System, Business Info System.
Question :-
Why should we consider Data Warehousing solutions?
When users are requesting access to a large amount of historical information for reporting purposes, you should strongly consider a warehouse or mart. The user will benefit when the information is organized in an efficient manner for this type of access.
Characteristics of DWH :-
    1. Subject Oriented
    2. Non Volatile
    3. Integrated
    4. Time Variant
Subject-oriented :-
    a. DWH is organized around variety subjects such as sales,product,customer.
    b. It helps decision makers to focuses on modeling and analysis of data.
    c. Excludes data not useful in decision support process.
Integration :-
    a. Data Warehouse is constructed by integrating multiple data marts.
    b. Data Preprocessing are applied to ensure consistency.
Time-variant :-
    a. Provides information bulk of older data to research
    b. Every key structure contains either implicitly or explicitly an element of time
Nonvolatile :-
    a. Data once recorded cannot be updated.
    b. Data warehouse requires two operations in data accessing
Three Data Warehouse Models :-
1. Enterprise warehouse :-
       a. collects all of the information about all subjects of all datamarts of the organization.
2. Data Mart :-
       a. a subset of corporate-wide data that is of value to a specific groups of users.  Its scope is confined to specific, selected groups, such as marketing data

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