In the Developer tool, you can configure some target columns as primary keys or foreign keys. Load order constraints ignore these keys. If the targets have primary key-foreign key constraints, you must define the load order constraints.

The Data Integration Service can stage the data to a local disk for the second target instance in a target load order constraint. When the mapping has multiple secondary target instances, the Data Integration Service loads the staged data to the targets without violating the constraints.

The Data Integration Service loads one target instance and then another target instance without determining whether the rows are inserts, deletes, or updates. For target tables with primary-key foreign-key constraints, an orphan row is a row in the foreign key target that does not have a matching row in the primary key target. The Data Integration Service does not check for orphan rows. The Data Integration Service loads all of the rows in the order you specify in the load order constraint.