When you run a mapping that uses an Aggregator transformation, the Data Integration Service creates an index cache and data cache in memory to run the transformation. If the Data Integration Service requires more space than available in the memory cache, it stores overflow data in cache files.
The Data Integration Service creates the following caches for the Aggregator transformation:
Index cache that stores group values as configured in the group by ports.
Data cache that stores calculations based on the group by ports.
The Data Integration Service does not use cache memory to run an Aggregator transformation with sorted ports. You do not need to configure cache memory for Aggregator transformations that use sorted ports.