It is Active transformation. If you configure the Sorter transformation for distinct output rows, the Mapping Designer configures all ports as part of the sort key. When the PowerCenter Server runs the session, it discards duplicate rows compared during the sort operation. \ Sorter Transformation is passive when the DISTINCT option is unchecked bcoz it wont change the number of records passes through it. Once the DISTINCT option is checked it may change the no of records if the records has duplicates.