if you enable the 'sorted I/option in AGG transformation, power centre server assumes that all data is sorted by group.
If you use sorted i/p and do not use the sorted data session fails.
When the 'Sorted Input' is enabled and if the data is not sorted, then unexpected results will occur. It means the
session will succeed but the end result may not be the way as per the business requirement.
Another point to be remembered is:Group by columns in the Aggregator transformation must be in the same order as they appear in the Sorter transformation
When you use sorted input,the integration service assumes all data is sorted by group.as the integration service reads rows for a group,it perform aggregate calculations.to,sorted Input option u must pass sorted data to agg t/r.
When you don't use sorted input,the integration service perform aggregate calculations as it rads. However, since data is not sorted,the Integration service stores data for each group until it reads the entire source to ensure all aggregate calculations r accurate