When you use sorted input, the Data Integration Service assumes all data is sorted by group and it performs aggregate calculations as it reads rows for a group. When required, the Data Integration Service stores group information in memory. To use the Sorted Input option, you must pass sorted data to the Aggregator transformation. If you use sorted input, the Aggregator transformation provides sorted output.

When you do not use sorted input, the Data Integration Service performs aggregate calculations as it reads. Because the data is not sorted, the Data Integration Service stores data for each group until it reads the entire source to ensure that all aggregate calculations are accurate.

For example, one Aggregator transformation has the STORE_ID and ITEM group by ports, with the sorted input option selected. When you pass the following data through the Aggregator, the Data Integration Service performs an aggregation for the three rows in the 101/battery group when it finds the group 201/battery:

If you use sorted input and do not presort data correctly, the Data Integration Service fails the mapping run.