Monday, 9 February 2015

Basic Oracle ETL Interview Questions and Answers

Below are some important Oracle ETL interview questions which are asked in most MNC company interviews for beginners or professionals.

11. What are the various tools? - Name a few?
A few are ....
- Abinitio
- DataStage
- Informatica
- Cognos Decision Stream
- Oracle Warehouse Builder
- Business Objects XI (Extreme Insight)
- SAP Business Warehouse
- SAS Enterprise ETL Server

12. What is latest version of Power Center / Power Mart?
The Latest Version is 7.2

13. What is the difference between Power Center & Power Mart?
PowerCenter - ability to organize repositiries into a data mart domain and share metadata across repositiries.
PowerMart - only local repositiry can be created.

14. What are the various transformation available?
Aggregator Transformation
Expression Transformation
Filter Transformation
Joiner Transformation
Lookup Transformation
Normalizer Transformation
Rank Transformation
Router Transformation
Sequence Generator Transformation
Stored Procedure Transformation
Sorter Transformation
Update Strategy Transformation
XML Source Qualifier Transformation
Advanced External Procedure Transformation
External Transformation

15. What is ODS (operation data source)?
ODS - Operational Data Store.
ODS Comes between staging area & Data Warehouse. The data is ODS will be at the low level of granularity.
Once data was poopulated in ODS aggregated data will be loaded into into EDW through ODS.

16. What is the difference between etl tool and olap tools?
ETL tool is ment for extraction data from the legecy systems and load into specified data base with some process of cleansing data.
ex: Informatica,data stage ....etc
OLAP is ment for Reporting OLAP data avaliable in Mulitidimectional model. so that u can write smple query to extract data fro the data base.
ex: Businee objects,Cognos....etc

17. What is the metadata extension?
Informatica allows end users and partners to extend the metadata stored in the repository by associating information with individual objects in the repository. For example, when you create a mapping, you can store your contact information with the mapping. You associate information with repository metadata using metadata extensions.
Informatica Client applications can contain the following types of metadata extensions:
Vendor-defined. Third-party application vendors create vendor-defined metadata extensions. You can view and change the values of vendor-defined metadata extensions, but you cannot create, delete, or redefine them.
User-defined. You create user-defined metadata extensions using PowerCenter/PowerMart. You can create, edit, delete, and view user-defined metadata extensions. You can also change the values of user-defined extensions.

18. What are the various test procedures used to check whether the data is loaded in the backend, performance of the mapping, and quality of the data loaded in INFORMATICA?
The best procedure to take a help of debugger where we monitor each and every process of mappings and how data is loading based on conditions breaks.

19. I am new to SAS, can anybody explain the process of extracting data from source systems,storing in ODS and how data modelling is done?
There are various ways of Extracting Data from Source Systems.For example , You can use a DATA step, an Import Process .It depends with your input data styles. What kind of File/database it is residing in. Storing ur data in an ODS can be done thru an ODS stmt/export stmt/FILE stmt, again which depends on the file & data format ,You want your output to be in.

20. Techniques of Error Handling - Ignore, Rejecting bad records to a flat file, loading the records and reviewing them (default values)?
Rejection of records either at the database due to constraint key violation or the informatica server when writing data into target table.These rejected records we can find in the badfiles folder where a reject file will be created for a session.we can check why a record has been rejected.And this bad file contains first column a row indicator and second column a column indicator.
These row indicators or of four types
D-valid data,
O-overflowed data,
N-null data,
T- Truncated data,
And depending on these indicators we can changes to load data successfully to target.
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