I also like the idea of utilizing a staging table to get your latest data into the database without interrupting data access.

Furthermore, you might consider using the MERGE INTO syntax to allow SQL Server to reconcile the differences and commit DML changes to the primary data table to reduce the amount of changes occurring only to what is actually different. This should reduce the amount of activity amongst all related indexes, triggers, etc and again allow the table to stay online for queries. Unfortunately, I've not attempted MERGEs on such a large data set, so by all means test and report back to us. 🙂

--Chris