On Wed, May 25, 2016 at 10:21 AM, Greg Dyck <[email protected]> wrote: > On 5/25/2016 6:51 AM, Peter Hunkeler wrote: >> >> So, just to be sure my memory is correct: On the hardware, the C, K and D >> fields are separate blocks of data separated by GAPs, right? It is only >> DFdss that combines the when printing. > > > Yes and no. On true physical CKD devices that would be true. On today's > emulated devices it isn't. > > I believe that DFDSS PRINT uses a Read-count-key-data command CCW to read > data. The count, key, and data would be then be combined and returned by the > control unit as a single block of data which is subsequently formatted by > DFDSS. > > Greg > Even when we had real CKDs with gaps, the memory buffers were adjacent. The lengths were in the count area.
https://en.wikipedia.org/wiki/Count_key_data -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
