When you create a mapping in advanced mode, you can preview data for individual transformations to test the mapping logic. The preview job runs on an
advanced cluster
in an AWS or Azure cloud environment and uses on-demand instances.
You can preview data if there are no mapping validation errors in the selected transformation. A mapping in advanced mode shows preview data for the selected transformation.
You can't preview data for the following transformations:
Sources that have binary fields
Normalizer
Router
Hierarchy Processor with multiple output groups
Target
If the cluster is running many jobs, the preview job might be slow.