Error Message : EXP_19183 User-defined function <user-defined function> uses an aggregator function
User Defined function (I hope you know what it is, if not check the link) is used in expressions to reuse expression logic and build complex expressions. In a user defined function if you use a Aggregator function then you will get the above error.
So better not to use Aggregator Function in the User Defined function syntax.
Error Message : SM_7072 Aggregate Error: Expecting keys to be descending.
You get this error when you check the Sorted Input option in an Aggregator transformation and the incoming data into the Aggregator is not sorted.So either you give sorted data or clear the Sorted Input option
Error Message : TT_11013 Aggregate Transformation: Error in parsing group-by ports.
In Aggregator there is an option to group rows. Normally grouping is done on unique rows, but when you try to group an Aggregator expression then this error will be thrown.
Error Message : TT_11014 Aggregator Transformation: Error in parsing output ports.This error comes when the Aggregator transformation in the mapping contains an invalid expression or port. You can validate the mapping and easily Debug this
Error Message : SM_7051 Aggregate error: index file timestamp is earlier than the timestamp of the Aggregator transformation or mapping.
After you modify the Aggregator Transformation and try to run the incremental aggregation session then the Integration Service may reuse the existing cache file that is invalid now (due to Aggregator modifications) then we get this error