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GeekInterview.com > Interview Questions > Data Warehousing
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Question: What is the difference between mapping parameter & mapping variable in data warehousing?
What are the types of variable available in data warehousing?
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| July 07, 2008 11:12:20 |
#3 |
| fir_dan |
Member Since: July 2008 Total Comments: 2 |
RE: What is the difference between mapping parameter & mapping variable in data warehousing?What are the types of variable available in data warehousing?
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A mapping parameter is a static value that you define before running the session and it retains the same value till the end of the session. Define a parameter in paramaeter file (.par) and use it in mapping or maplet and when PowerCenter server the runs the session it evaluates the value from the parameter and retains the same value throughout the session. When the session run again it reads from the file for its value.
A mapping variable is dynamic or changes anytime during the session. PowerCenter reads the intial value of the variable before the start of the session and changes its value by using variable functions and before ending the session its saves the current value (last value held by the variable). Next time when the session runs the variable value is the last saved value in the previous session. For example if you have a count variable that it gets incremented every time a session is run, the variable will have a value of 3 on its 4th run. The variable value will not be saved by the session when it fails or when it is configured for a test load or when it runs on a debug mode. There is also another option not save the variable value at the end of the session by discarding session output so it that everytime it starts it will take the intial value not the last saved value.
Thanks,
Dani.
A variable type is defined based on its aggregation viz count, min and max. Informatica give three functions for the three variable functions for each of this type SetCountVariable, SetMaxVariable, SetMinVariable. It also limits the datatypes used within these types like the count type can have only integer and small integer datatypes where as min and max can use any datatype. A variable cannot use a binary datatype. |
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