[ ] never delete intermediate data : even if intermediate data doesn't seem usefull, never delete a table or a file : it can be used as a savepoint. 1To = 60 $ = 2 hours of your time => if you delete a 10 Go file from your process to save space, it's worth only if it takes you less than a minute to get the file back
[ ] Don't write a rollback yourself, trust your framework : if you have programmed a script that transform data, and have well tested it in dev, and in integration environements, and it fails in production... How much do you trust a rollback script ? You should rely on database transacations, tuttle or disks snapshots