On 12 September 2014 10:38, Anne & Lynn Wheeler <l...@garlic.com> wrote: > however, ibm CKD dasd had a peculiar power failure mode ... that might > occur in the middle of a write operation ... there would be sufficient > power to complete a write in progress ... but not sufficient power to > continue transmitting the data from processor memory over the channel > ... so the controller completed the write operation with all zeros (and > no indication of a read/write failure). As far as i know, none of the > other mainframe systems made any software provisions to handle this > particular failure mode of ibm ckd dasd.
That's a not unreasonable implementation of an architected behaviour on the B&T/OEMI channel to CU interface, independent of power failure. If an I/O reset is received by the control unit while a write is in progress, it completes the write with zeros. What would be a more reasonable behaviour on a disk with little or no buffering? So in theory it's possible to corrupt data on disk just by hitting System Reset (or Load) during a disk write. If you look at the probability it's pretty unlikely, but I worked at one place that had a strict rule about hitting stop and waiting a few seconds before doing the reset or load. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
