In large numbers, transformation errors slow the performance of the Integration Service. With each transformation error, the Integration Service pauses to determine the cause of the error and to remove the row causing the error from the data flow. Next, the Integration Service typically writes the row into the session log file.
Transformation errors occur when the Integration Service encounters conversion errors, conflicting mapping logic, and any condition set up as an error, such as null input. Check the session log to see where the transformation errors occur. If the errors center around particular transformations, evaluate those transformation constraints.
If you do not set the error threshold, the Integration Service continues to process error rows, thereby increasing the session run time. To optimize performance, set the error threshold to stop the session after a set number of row errors.
If you need to run a session that generates a large number of transformation errors, it is possible to improve performance by setting a lower tracing level. However, this is not a recommended long-term solution to transformation errors.