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Top 25 Informatica Interview Questions with answers 2014/15


Top 25 Informatica Interview Questions with answers 2014/15
Top 25 Informatica Interview Questions and answers.Latest  Data warehouse BI Interview Questions. Informatica Interview Questions 2015. Latest Informatica Interview Questions with answers. 



1.What is Data warehouse?
 
In 1980, Bill Inmon known as father of data warehousing. "A Data warehouse is a subject oriented, integrated ,time variant, non volatile collection of data in support of management's decision making process".
Subject oriented : means that the data addresses a specific subject such as sales, inventory etc.
Integrated : means that the data is obtained from a variety of sources.
Time variant : implies that the data is stored in such a way that when some data is changed.
Non volatile : implies that data is never removed. i.e., historical data is also kept.
 

2. What is the difference between database and data warehouse?
   
A database is a collection of related data. A data warehouse is also a collection of information as well as a supporting system.

or

In Data base we can maintain only current data which was not more than 3 years But in datawarehouse we can maintain history data it means from the starting day of enterprise DDL commands it means ( Insert ,update,delete)we can do in Database In datawarehouse once data loaded in Datawarehouse we can do any DDL operatations

3. What are the benefits of data warehousing?
 
Historical information for comparative and competitive analysis.

Enhanced data quality and completeness.

Supplementing disaster recovery plans with another data back up source.

  
4. What are the types of data warehouse?
 
There are mainly three type of Data Warehouse are :

Enterprise Data Warehouse
Operational data store
Data Mart

5. What is the difference between data mining and data warehousing?

Data mining, the operational data is analyzed using statistical techniques and clustering techniques to find the hidden patterns and trends. So, the data mines do some kind of summarization of the data and can be used by data warehouses for faster analytical processing for business intelligence.
Data warehouse may make use of a data mine for analytical processing of the data in a faster way.


6. What is the benefit of partitioning a session?

Partitioning a session means solo implementation sequences within the session. It’s main purpose is to improve server’s operation and efficiency. Other transformations including extractions and other outputs of single partitions are carried out in parallel.

7. How are indexes created after completing the load process?

For the purpose of creating indexes after the load process, command tasks at session level can be used. Index creating scripts can be brought in line with  the session’s workflow or the post session implementation sequence. Moreover this type of index creation cannot be controlled after the load process at transformation level.

8. Explain sessions. Explain how batches are used to combine executions?

A teaching set that needs to be implemented to convert data from a source to a target is called a session. Session can be carried out using the session’s manager or pmcmd command. Batch execution can be used to combine sessions executions either in serial manner or in a parallel. Batches can have different sessions carrying forward in  a parallel or serial manner.

9. How many number of sessions can one group in batches?

One can group any number of sessions  but it would be easier for migration if the number of sessions are lesser in a batch.

10. Explain the difference between mapping parameter and mapping variable?

When  values  change during the session’s execution it’s called a mapping variable. Upon completion the Informatica server stores the end value of a variable and is reused when session restarts. Moreover those values that do not change during the sessions execution are called mapping parameters.  Mapping procedure explains mapping parameters and their usage. Values are allocated to these parameters before starting the session.

11.What is complex mapping?

Following are the features of complex mapping.

Difficult requirements
Many numbers of transformations
Complex business logic

12. How can one identify whether mapping is correct or not without connecting session?

One can find whether the session is correct or not without connecting the session is with the help of debugging option.

13. Can one use mapping parameter or variables created in one mapping into any other reusable transformation?

Yes, One can do because reusable transformation does not contain any mapplet or mapping.

14. Explain the use of aggregator cache file?

Aggregator transformations are handled in chunks of instructions during each run. It stores  transitional values which are found  in local buffer memory. Aggregators provides extra cache files for storing the transformation values if extra memory is required.

15. Briefly describe lookup transformation?

Lookup transformations are those transformations which have admission right to RDBMS based data set. The server makes the access faster by using the lookup tables to look  at explicit table data or the database. Concluding data is achieved by matching the look up condition for all look up ports delivered during transformations.

16. What does role playing dimension mean?

The dimensions that are utilized for playing diversified roles while remaining in the same database domain are called role playing dimensions.

17. How can repository reports be accessed without SQL or other transformations?

Ans:Repositoryreports are established by metadata reporter. There is no need of SQL or other transformation since it is a web app.

18. What are the types of metadata that stores in repository?

The types of metadata includes Source definition, Target definition, Mappings, Mapplet, Transformations.

19. Explain the code page compatibility?

When data moves from one code page to another provided that both code pages have the same character sets then data loss cannot occur. All the characteristics of source page must be available in the target page. Moreover if  all the characters of source page are not present in the target page then it would be a subset and data loss will definitely occur during transformation due the fact the two code pages are not compatible.

20. How can you validate all mappings in the repository simultaneously?

All the mappings cannot be validated simultaneously because each time only one mapping can be validated.

21. Briefly explain the Aggregator transformation?

It allows one to do aggregate calculations such as sums, averages etc. It is unlike expression transformation in which  one can do calculations in groups.

22. Describe Expression transformation?

Values can be calculated in single row before writing on the target in this form of transformation. It can be used to perform non aggregate calculations. Conditional statements can also be tested before output results go to target tables.

23. What do you mean by filter transformation?

It is a medium of filtering rows in a mapping. Data needs to be transformed through filter transformation and then filter condition is applied.  Filter transformation contains all ports of input/output, and the rows which meet  the condition can only pass through that filter.

24. What is Joiner transformation?

 Joiner transformation combines two affiliated heterogeneous sources living in different locations while a source qualifier transformation can combine data emerging from a common source.

25. What is Lookup transformation?

 It is used for looking up data in a relational table through mapping. Lookup definition from any relational database is imported from a source which has tendency of connecting client and server. One can use multiple lookup transformation in a mapping.







 
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