Friday, November 14, 2008

Informatica Interview Questions And Answers V

What r the tasks that Loadmanger process will do?
Manages the session and batch scheduling: Whe u start the informatica server the load maneger launches and queries the repository for a list of sessions configured to run on the informatica server.When u configure the session the loadmanager maintains list of list of sessions and session start times.When u sart a session loadmanger fetches the session information from the repository to perform the validations and verifications prior to starting DTM process.
Locking and reading the session: When the informatica server starts a session lodamaager locks the session from the repository.Locking prevents U starting the session again and again.
Reading the parameter file: If the session uses a parameter files,loadmanager reads the parameter file and verifies that the session level parematers are declared in the file
Verifies permission and privelleges: When the sesson starts load manger checks whether or not the user have privelleges to run the session.
Creating log files: Loadmanger creates logfile contains the status of session.
What are the different types of transformation available in informatica. and what are the mostly used ones among them
Mainly there are two types of tranformation.1]Active TransformationAn active transformation can change the number of rows that pass through it from source to target i.e it eliminates rows that do not meet the condition in transformation.2]Passive TransformationA passive transformation does not change the number of rows that pass through it i.e it passes all rows through the transformation.Transformations can be Connected or UnConnected. Connected TransformationConnected transformation is connected to other transformations or directly to target table in the mapping.UnConnected TransformationAn unconnected transformation is not connected to other transformations in the mapping. It is called within another transformation, and returns a value to that transformation.list of Transformations available in Informatica:1 source qualifier Tranformation2..Expression Transformation 3..Filter Transformation 4..Joiner Transformation 5..Lookup Transformation 6..Normalizer Transformation 7..Rank Transformation 8..Router Transformation 9..Sequence Generator Transformation 10..Stored Procedure Transformation 11..Sorter Transformation 12..Update Strategy Transformation .13...Aggregator Transformation 14..XML Source Qualifier Transformation 15..Advanced External Procedure Transformation 16..External Transformation 16.. custom tranformationMostly use of particular tranformation depend upon the requirement.In our project we are mostly using source qualifier ,aggregator,joiner,look up transformation
What are two types of processes that informatica runs the session?
Load manager Process: Starts the session, creates the DTM process, and sends post-session email when the session completes.
The DTM process. Creates threads to initialize the session, read, write, and transform data, and handle pre- and post-session operations.
How can we store previous session logs
ust run the session in time stamp mode then automatically session log will not overwrite current session log.
What is meant by Junk Attribute in Informatica?
Junk Dimension A Dimension is called junk dimension if it contains attribute which are rarely changed ormodified. example In Banking Domain , we can fetch four attributes accounting to a junk dimensions like from the Overall_Transaction_master table tput flag tcmp flag del flag advance flag all these attributes can be a part of a junk dimensions
In a joiner trasformation, you should specify the source with fewer rows as the master source. Why?
Joiner transformation compares each row of the master source against the detail source. The fewer unique rows in the master, the fewer iterations of the join comparison occur, which speeds the join process.
What r the tasks that source qualifier performs?
Join data originating from the same source database. You can join two or more tables with primary-foreign key relationships by linking the sources to one Source Qualifier.
Filter records when the Informatica Server reads source data. If you include a filter condition, the Informatica Server adds a WHERE clause to the default query.
Specify an outer join rather than the default inner join. If you include a user-defined join, the Informatica Server replaces the join information specified by the metadata in the SQL query.
Specify sorted ports. If you specify a number for sorted ports, the Informatica Server adds an ORDER BY clause to the default SQL query.
Select only distinct values from the source. If you choose Select Distinct, the Informatica Server adds a SELECT DISTINCT statement to the default SQL query.
Create a custom query to issue a special SELECT statement for the Informatica Server to read source data. For example, you might use a custom query to perform aggregate calculations or execute a stored procedure.

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