Export-Delete-Load-Calculate
We had an OLAP database that needed recalculating every 3 hours (month end financials). OLAP back then was slow and recalculating a full cube was "inefficient" - it would take 4 hours. Exporting the bottom rows (i.e. source data) dropping the database and reloading needed about 40 minutes.
So, export, delete, load and calculate it was...
Except, one day, I started with the second step instead... AARGH!
My colleague said, just load the previous export and blame it on the users! Instead, I had a quick word with the finance manager, explained the situation, restored from the previous export and then replayed the transaction log. We got all but 4 entries back! I was applauded for my honesty... Its great having a good boss.