On Wednesday, 01/31/2007 at 03:57 CST, "McKown, John" <[EMAIL PROTECTED]> wrote: > Have you looked at SAE? It has a stand-alone ERASE capability. You can > even IPL it off of the DVD in the HMC! Or DASD or Tape.
I find such products ... interesting. If you look at the S/390 Command Reference for ESS (SHARK), you will find that the ERASE CCW or formatting record 0 of a track are documented to "erase" data. But when you read what it says about erasure, things get fuzzy. To wit: "A record is said to be erased when it is rendered incapable of being read by the commands and facilities normally used for reading recorded data from the device. The manner in which the erase operation is performed is overwriting the record referenced with pad characters and then erasing the remainder of the track." Of course, it uses the word "erase" in the definition of the operation, so who knows what it will do. Consider, too, that modern drives separate the appearance of ECKD from reality. It can simply mark some metadata that says "erased" which the microcode will respect. But take the RAID drives out and read them elsewhere, and who knows what you will find. Then there's that nasty word "normally used" in there. It makes me nervous. And if you have a moving cursor algorithm, rewriting the "same" record may not, in fact, rewrite the same record. It may get written and then index pointers are updated. I find lots of information about "data security erase" for tapes, but not for disks. Methinks I must contact a Reverened Engineer to find out what gives these days... Alan Altmark z/VM Development IBM Endicott
