Hi,
it won't impact on any performance issue unless.
lets say example will create the query on cube but query executing time taking we need to create the aggregates and BIA.
it will improve the performance.
in BW system it self required the more processer (SM51)
while extracting data form ERP to BW you will create the generic data source based on the function module - it will improve the performance.
very good documents avilable at SCN, please find the below docs.
House Keeping / Performance Tuning Activities in SAP BW Systems -- PART 1
Thanks,
Phani.