Read the thread statistics and work time statistics in the session log. When the Integration Service spends more time on the transformation thread than the writer or reader threads, you have a transformation bottleneck. When the Integration Service spends more time on one transformation, it is the bottleneck in the transformation thread.

Analyze performance counters. High errorrows and rowsinlookupcache counters indicate a mapping bottleneck.

Add a Filter transformation before each target definition. Set the filter condition to false so that no data is loaded into the target tables. If the time it takes to run the new session is the same as the original session, you have a mapping bottleneck.