I don't understand Alan's reply. Isn't the mdisk cache always a R/O
cache. Aren't all dasd writes done to the dasd and not to the MDC? Isn't
FLASHCOPY going to reflect the real contents of the dasd at the time of the
copy. I know that there can be differences between what is actually
written on a mdisk directory and what the writer of the mdisk has in memory
until the disk is released, but that isn't a MDC consideration, I don't think.
Jim
At 10:26 AM 12/6/2005, you wrote:
On Monday, 12/05/2005 at 11:36 CST, Tom Duerbusch
<[EMAIL PROTECTED]> wrote:
> I have been using flashcopy for some interm backups that I restore from,
> also using flashcopy.
>
> So, if I have been using device 150, and I do a flashcopy from 1150 to
> 150, what happens to the MDC contents for 150?
If you use the CP FLASHCOPY command or a guest initiates a "virtual"
flashcopy I/O, CP will handle the cache.
If you go behind CP's back to do the flashcopy from the disk controller
console then you are in trouble. The controller does not notify the host
of "background" activity on a volume and the cache will not be valid. So,
if you use the controller console be sure to SET MDC FLUSH <vdev> before
you start reading/writing the minidisk again.
Obviously it is far better to initiate a flashcopy from CP.
Alan Altmark
z/VM Development
IBM Endicott
Jim Bohnsack
Cornell Univ.
(607) 255-1760
