What is Incremental Aggregation?
We can enable the session option, Incremental Aggregation for a session that includes an Aggregator Trans-formation. When the Integration Service performs incremental aggregation, it actually passes changed source data through the mapping and uses the historical cache data to perform aggregate calculations incrementally.
Sorted input for aggregator transformation will improve performance of mapping. How-ever, if sorted input is used for nested aggregate expression or incremental aggregation, then the mapping may result in session failure. Explain why?
|Interview questions on aggregator transformation in informatica - Part - 4|
In case of a nested aggregation, there are multiple levels of sorting associated as each aggregation function will require one sorting pass, and after the first level of aggregation, the sort order of the group by column may get jumbled up, so before the second level of aggregation, Informatica must internally sort it again. However, if we already indicate that input is sorted, Informatica will not do this sorting - resulting into failure. In incremental aggregation, the aggregate calculations are stored in historical cache on the server. In this historical cache the data may not be in sorted order. If we give sorted input, the records come as presorted for that particular run but in the historical cache the data may not be in the sorted order.
How can we delete duplicate record using Informatica Aggregator?
One way to handle duplicate records in source batch run is to use an Aggregator Transformation and using the Group By checkbox on the ports having duplicate occurring data. Here you can have the flexibility to se-lect the last or the first of the duplicate column value records.