The previous articles in the series describe why we can't use the truncate and reload scenario in detail. The short story is that this is a multi-tenant system and we don't want to clear out the other customer's data (From previous loads in the past and earlier in the same day). Also for our large fact tables the data is too large to load for all customer's completely daily (which is what a truncate and reload would require). For some of the fact tables the source system doesn't carry history, so we could not do a full reload every day even if we wanted to.