OLAP 
>Online Analytical Processing (OLAP) is a popular and 
powerful data analytical method.
>It explores the complex data structure and presents the 
information 
OLAP functionality is:
•	Multidimensional -- OLAP services provide a wide 
variety of possible views or a multidimensional conceptual 
view of the data by supporting a dimensional aggregation 
path or hierarchies and/or multiple hierarchies. 
•	Easy to understand -- The data mart designed for 
OLAP analysis should handle any business logic and 
statistical analysis that is relevant to the application 
and the developer, while at the same time, keeps it easy 
enough for the target user. 
•	Interactive -- OLAP helps the user combine business 
information through comparative,. The users are allowed to 
define new ad hoc calculations as part of the analysis and 
can report on the data in any desired way. 
•	Fast -- OLAP services are usually implemented in a 
multi-user client/server mode and offer consistently rapid 
responses to queries, regardless of database size and 
complexity. 

Dw:historical data for related application and this is 
support to decision making system. 

Eg: sales manager check the total sale details for all 
loaction. every location using seperate database. so we 
need to merge all data in one database.

- we can use star schema or snowflake shema

OLAP : online analtical processing.