When you define columns by mapping flow, target columns are determined by upstream transformations. When an upstream transformation changes the port order and metadata, the Write transformation picks up the changes.
You can retain keys when you create or replace the target if the key columns in the upstream transformation match the key column names in the target.
The following image shows how the Write transformation appears when you define target columns based on mapping flow:
To avoid unexpected results, do not configure a run-time link to a Write transformation that defines targets based on the mapping flow.
Configure this functionality on the
Ports
tab of the Write transformation for flat file and relational targets.