ETL tool Interview questions

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.
 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.

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.

Where do we use connected and un connected loops
If return port only one then we can go for unconnected. More than one return port is not possible with Unconnected. If more than one return port then go for Connected.

Where do we use connected and un connected lookups
If return port only one then we can go for unconnected. More than one return port is not possible with Unconnected.  If more than one return port then go for Connected. 

Where do we use semi and non additive facts
Additve: A masure can participate arithmatic calulatons using all or any demensions.
Ex: Sales profit
Semi additive: A masure can participate arithmatic calulatons using some demensions.
Ex: Sales amount
Non Additve:A masure can’t  participate arithmatic calulatons using demensions.
Ex: temparature

What is Entity relation?? How is works with Datawarehousing ETL modeling
:Entity is nothing but an Object, it has characteristics.We call entity in terms of Logical view.The entity is called as a table in terms of Physical view.
The Entity relationship is nothing but maintaining a primary key,foreign key relation between the tables for keeping the data and satisfying the Normal form.
There are 4 types of Entity Relationships.
1.One-One, 2.One-Many, 3.Many-One 4.Many-Many
In the Datawarehouse modeling Entity Relationship is nothing but,a Relationship between dimension and facts tables(ie:Primary,foreign key relations between these tables).
The fact table getting data from dimensions tables because it containing primary keys of dimension tables as a foreign keys for getting summarized data for each record.

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