42. DWH FAQ's

1) What is Data warehouse?
Data warehouse is relational database used for query analysis and reporting. By definition data warehouse is Subject-oriented, Integrated, Non-volatile, Time variant.
Subject oriented : Data warehouse is maintained particular subject.
Integrated : Data collected from multiple sources integrated into a
user readable unique format.
Non volatile : Maintain Historical date.
Time variant : data display the weekly, monthly, yearly.
2) What is Data mart?
A subset of data warehouse is called Data mart.
3) Difference between Data warehouse and Data mart?
Data warehouse is maintaining the total organization of data. Multiple data marts used in data warehouse. where as data mart is maintained only particular subject.
4) Difference between OLTP and OLAP?
OLTP is Online Transaction Processing. This is maintained current transactional data. That means insert, update and delete must be fast.
5) Explain ODS?
Operational data store is a part of data warehouse. This is maintained only current transactional data. ODS is subject oriented, integrated, volatile, current data.
6) Difference between Power Center and Power Mart?
Power center receive all product functionality including ability to multiple register servers and metadata across the repository and partition data.
One repository multiple informatica servers. Power mart received all features except multiple register servers and partition data.
7) What is a staging area?
Staging area is a temporary storage area used for transaction, integrated and rather than transaction processing.
When ever your data put in data warehouse you need to clean and process your data.
8) Explain Additive, Semi-additive, Non-additive facts?
Additive fact: Additive Fact can be aggregated by simple arithmetical additions.
Semi-Additive fact: semi additive fact can be aggregated simple arithmetical
additions along with some other dimensions.
Non-additive fact: Non-additive fact can’t be added at all.
9) What is a Fact less Fact and example?
Fact table which has no measures.
10) Explain Surrogate Key?
Surrogate Key is a series of sequential numbers assigned to be a primary key for the table.