All new columns added to the SAT must be added to the end of the Satellite HASHDIFF. Dan Linstedt describes this as, "Columns that are NULL and at the end of the table are not added to the input of the hash function"[1]. Basically this pattern prevents reloading of the entire dataset when there is a new column added to the SAT and is NULL for the historical records. Loading data into SAT that has not changed is an Anti-pattern.
- Linstedt, D. and Olschimke, M., 2016. Building a Scalable Data Warehouse with Data Vault 2.0. Morgan Kaufmann, p.369.