During a session, the Integration Service compares an input row with rows in the data cache. If the input row out-ranks a cached row, the Integration Service replaces the cached row with the input row. If you configure the Rank transformation to rank across multiple groups, the Integration Service ranks incrementally for each group it finds.
The Integration Service stores group information in an index cache and row data in a data cache. If you create multiple partitions in a pipeline, the Integration Service creates separate caches for each partition.