On 9/6/06, Wakser, David <[EMAIL PROTECTED]> wrote:
Please settle an argument: if a DASD volume is to be shared in WRITE
mode between two VSE systems running under VM, should the MDISK statement
specify MWV or MW?
Why settle... can we not just disagree? ;-)
If you have multiple systems on the same z/VM, you need MWV to make
sure that CP will intercept reserve / release and emulate it. You
could not have all virtual machines do real reserve release because
the hardware would not be able to distinguish between virtual machines
(only sees which LPAR does it).
When the virtual machines are on different LPARs (or machines) you
need the disk to start at cylinder 0 to ensure that CP will indeed
pass the reserve/release to the real device (and I am not sure whether
you have to define it as SHARED in the configuration file, but you
prolly want to disable MDC anyway).
When you more than one VSE in the z/VM LPAR and another one outside
the LPAR (native or under z/VM, same machine or other machine) you
need MWV *and* start at cyl 0 to make sure that CP will keep the
guests apart, and will issue the real reserve/release that comes from
that.
Rob
--
Rob van der Heij
Velocity Software, Inc
http://velocitysoftware.com/
