In a message dated 6/30/2005 3:48:28 P.M. Central Daylight Time, [EMAIL PROTECTED] writes: >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...
>Tom Kern 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. Bill Fairchild ---------------------------------------------------------------------- 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
