Constraints question

Let's say I'm using an "order_header" and "order_item" tables. There is a constraint between these tables. I need to unload the "order_header" from a database and load it into another database without deleting the "order_item" (the primary keys will not changed). If I use this code : begin work; delete from order_header; load from order_header.unl insert into order_header; commit work; Is there a way to have Informix checked the constraints at the "commit" instead than the "delete"? Thank you