Depending on the sensitivity of the data I would reccommend removing and destroying the disk drives. When we have gotten rid of an old AS400 that is what we have done. Since the OS license is non transferable and the potential new owner will have to purchase a copy of the OS from IBM or the machine is destined for the junkyard. There is only one fail safe way to make sure the data is non recoverable, destroy the disk drives. We take out to the parking lot and smash them with a sledge hammer. If you are not concerned that someone would try to recover the data, then you could simply use the system tools and reformat the hard drives. In caeses where the data wasn’t too sensitive and we knew the buyer like another sister company or an IS employee of many years we simply reformatted the hard drives and restored the operating system only. Believe me without extreme knowledge of the AS400 and lots of money recovering from formatting the drives is quite difficult. In addition there is a selection in the system tools for formatting the drives to the department of defense standards which actualy writes 0′s and 1′s to the drive multiple times, such that according to the department defense the previous data is no longer recoverable. The issue with this method is the amount of time it takes to format each drive. Depending on the age of the AS400 and the type of disk drive this can take more than 1 hour per drive. Hope this helps. Good luck.