It sounds as though your hands are tied and you don't really have good options. The only thing you haven't ruled out is to do a comparison of the data as you load it from Oracle to your staging server and don't write the data that has not changed to your staging target. I would use the hashbytes function rather than a checksum because it is less likely to have a colision of data. Also make sure you trim both your source and target when comparing the data.