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Tuesday, 22 September 2015

Interview questions on aggregator transformation in informatica - Part -2


By on 10:53:00


How does Aggregator Transformation handle NULL values?
 
Answer:


By default, the aggregator transformation treats null values as NULL in aggregate functions. But we can specify to treat null values in aggregate functions as NULL or zero.

 
What are the performance considerations when working with Aggregator Transformation?
 
Answer:


Interview questions on aggregator transformation in informatica
Interview questions on aggregator transformation in informatica
Filter the unnecessary data before aggregating it. Place a Filter transformation in the mapping be-fore the aggregator transformation to reduce unnecessary aggregation.

Improve performance by connecting only the necessary input/output ports to subsequent transformations, thereby reducing the size of the data cache.

Use Sorted input which reduces the amount of data cached and improves session performance.


Aggregator performance improves dramatically if records are sorted before passing to the aggregator and “Sorted Input” option under aggregator properties is checked. The record set should be sorted on those columns that are used in Group By operation.

It is often a good idea to sort the record set in database level e.g. inside a source qualifier transformation, unless there is a chance that already sorted records from source qualifier can again become unsorted before reaching aggregator.



What are the uses of index and data cache?
Answer:
 
The group data is stored in index files whereas Row data stored in data files.



What differs when we choose Sorted Input for Aggregator Transformation?


Answer:

Integration Service creates the index and data caches files in memory to process the Aggregator transformation. If the Integration Service requires more space as allocated for the index and data cache sizes in the transformation properties, it stores overflow values in cache files i.e. paging to disk.

One way to increase session performance is to increase the index and data cache sizes in the transformation properties.

But when we check Sorted Input the Integration Service uses memory to process an Aggregator transfor-mation it does not use cache files.

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