I went back to check the source code for the program I have for doing this level of 'CLEARING' a DASD. It does indeed write a record to allow the DASD to be used by subsequent users.
CYL 00000000 HD 00 HOME ADDRESS 0000000000 RECORD ZERO 0000000000 00 0008000000 00 00000000 CYL 00000000 HD 00 REC 001 COUNT 0000000001 00 0000 /Tom Kern --- Bill Fairchild <[EMAIL PROTECTED]> wrote: > >A re-write of HOME ADDRESS for each track, chaining together I/Os to > logically > >reset 1 3380/3390 cylinder with each I/O might be sufficient in a DR > situation... > > Technically correct, practically not such a good idea, though. This will > indeed erase all tracks in one cylinder if 15 home address rewrites are > chained > together per I/O. But it will also cause massive problems when the next > user tries to unload data onto the tracks, as there will be no R0 on any of > the > tracks. You must rewrite Home Address AND R0 in order to leave the tracks > both erased AND also usable by anyone else. Or you could simply rewrite > only > the R0 blocks. If you are going to go to the trouble to write an ALC > program > to do this, then you might as well skip over the home address and R0 and > write an EOF record where the first record (normally known as R1) would be. > This > would reduce channel connect time to a very low value per track and still > erase the rest of the track. > > In order to rewrite the home address and/or R0, the program doing so must be > > authorized, but it must be authorized anyway if you are going to erase tracks > > allocated to any users to which the erasing job does not have write access. > > The more things like home address and R0 you try to erase, the more likely > you are to hose the track so that no one else can use it until an ICKDSF > fixes it. It's better to rewrite the R1 block with a very small piece of > useless > data (one byte of X'00' or an EOF record, e.g.). You can hose R1 and the > track can still be used by others. > > It's necessary but not sufficient to erase your data. You must also leave > the tracks in a condition usable by the next user, or you may be asked to > find > a different DR site next time. > > > where you can trust that the DASD will be reused soon and often before it > gets > > removed. > > DASD doesn't get removed any more, at least not by any users. An engineer > might remove one if it needs repair or replacement. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
