SAP BW Basics --1

Q:- What is STAR Schema?   Ans:- A Fact Table at the center and surrounded (linked ) by dimension Table.
 
Q:- What is a slowly changing dimension?  Ans:- A dimension containing a characteanristics which changes over a time ; for example take employee job title ; this changes over a period of time with different job titles.

Q:-What are the Advantages of Extended STAR Schema Vs. the Star Schema?Use of generated keys(numeric) for faster access.
External Hierarchy.
Multilanguage support.
Master Data common to all cubes.
Slowly changing dimension support.
aggregates in its own table for faster access.

Q. What is an external hierarchy?
Ans. Presentation hierarchies are stored in its own tables(hierarchy tables) for characteristic values.

Q.What are time dependent text/attributes of a characteristic?
Ans. If the text(for example name of a product/person
Over a time)or if the attribute changes over a time( for example job title) then these must be marked as time dependent.

Q.Can you create your own time characteristics?
Ans. No.

Q.what are the types of attributes?
Ans.Display only and navigational; display only attributes are only for display and no analysis can be done ;navigational attributes can behave like regular characteristics; for example assume that we have customer characteristics with country as navigational attribute; you can analyse the data using customer and country.

Q. what is alpha conversion?
Ans.Apha conversion is used to store data consistently by storing any numeric values by prefixing 0s; for example if you defined any material as 6 numeric then number 1 is stored as 000001 but displayed as 1; this removes inconsistency between 01 vs. 001.

Q. what is the alpha check execution programme?
Ans.This is used to check consistency for BW 2.x before upgrading the system to 3.x; the transaction is RSMDCNVEXIT.

Q.What is the attribute only flag?
Ans.If the flag is set, no master data is stored; this is only used as the attribute for other characteristics; for example comments on a AR document.

Q.What is compounding?
Ans.This defines the superior info object which must be combined to define object; for example when you define cost centre then controlling area is the compounding (superior) object.

Q.What is the Bex options for characteristics like F4 help for querry definition and execution?
Ans.This defines how the data is displayed in query definition screen or when query is executed; options are from the data displayed, from master data table ( all data) and from dimension data; for example let us assume that you have 100 products in all, and 10 products in a cube; in bex you display the query for 2 products; the following options for products will display different data
a.selective data only - will display 2 products
b.dimension data -will display 10 products
c.from master data - will display all 100 products