Schema changes can impact your ETL process. The following table describes the impact of various schema changes.

Table 1. Schema change impacts
Source Table Change Table (C) Change Tracking Table (CT) ETL
Add a field No record No record No action required.
Add a field policy which is a new field in source table New field Record written indicating Field Add Existing ETL program continues to work. You can use CT record to know if this action occurred and decide to alter ETL.
Delete field (offline) Rename field on Chg Tbl (offline) causes CRC issue on ETL process ** Record written indicating Field Delete Existing ABL ETL will fail with a CRC issue immediately. If SQL ETL references the deleted field name it will fail. There can be dynamic use of the CT record indicating field delete.

Delete field policy

(Create a new policy without a field), source field still exists

 Field exists with old name Record written indicating Field Delete ETL can use bitmap to indicate which fields can be extracted.
Re-add field policy with change field already in Change Table Field exists Record written indicating Field Add Existing ETL program continues to work. You can use CT record to know if this action occurred and decide to alter ETL.
Add field policy with existing field name in source table New field in the change table Record written indicating Field Add Existing ETL program continues to work. You can use CT record to know if this action occurred and decide to alter ETL.
Re-add field and field policy with same name as was previously dropped New field with the same name added(online) Record written indicating Field Add Use CT record to know if action occurred
Rename field on source same as Change field that was deleted with ABL special naming convention No action
Rename field on source that already has a change field Field renamed Existing ETL will be effected by a CRC change caused by rename.