Yes, I knew about the basic operation, I just don't see why the logic
should be restricted to full pack minidisks (except maybe to prevent
potential problems when somebody defines multiple MWV minidisks
on the same pack ..).
But thanks for confirming the documented operation!
Eginhard Jaeger
On Wed, Jul 28, 2010 at 4:43 PM, Bruce Hayden <[email protected]> wrote:
Yes, this is true. RACF manages the updates to the shared database
using the reserve/release functions of the DASD control unit. So, a
reserve issued by RACF must flow to the real control unit, so that any
reserve issued by another system would be rejected until a release is
done. And, CP only issues a hardware RESERVE to a volume only when
all of these conditions are met:
(a) the device is a full-pack minidisk
(b) the MDISK has link mode MWV
(c) the device is marked as 'shared' whether by SET SHARED or via
RDEVICE statement in SYSTEM CONFIG
A dedicated device works also. CSE (xlink) is *not* sufficient (or
required for RACF), because that only controls links to minidisks, not
reserve/release on a multiple-write minidisk.
On Wed, Jul 28, 2010 at 10:02 AM, Eginhard Jaeger <[email protected]>
wrote:
Is that really true? When checking just now I found that the 'Planning
and Administration' manual also says so, but I'm 99% sure (allowing
1% for memory deterioration) that I shared a 20 cyl. RACF database
between two separate VM XA systems and it worked perfectly well.
While the rest of the packs certainly shouldn't be used for any high
activity stuff I believe we did actually use it (space was still quite
expensive 20 years ago).
So I suspect that the 'full pack' requirement may just come from sharing
DASD with non-VM systems, and that it doesn't really apply to the
RACF data base being shared between multiple VM systems only.
But I never had to share disks for later VM releases and so don't know
for
sure ..
Eginhard Jaeger
From: "Bruce Hayden" <[email protected]>
That will not work. The database must be on full pack minidisks,
which means the minidisk must start at cylinder 0 and go to the end of
the volume. (DEVNO minidisks can also be used.) So, your directory
entries must be:
MDISK 200 3390 0 END VMRACP MWV READ WRITE MULT
MDISK 300 3390 0 END VMRACB MWV READ WRITE MULT
The devices must be defined in your SYSTEM CONFIG file as shared.
