| Hi John,
In Version 1.0 of VDC, the only functionality we are shipping is the
ability to flush all of the volumes that are currently mounted on the
local node. It will flush the local cache only. In other words, the
V1.0 syntax will be just:
$ FLUSH
The optional parameter and the /CLUSTER qualifier appear at V2.0.
The idea of going in on SET VOLUME appeals, but I don't see how it
can cope with the V1.0 VDC functionality. All I can think of
is having a qualifier like /FLUSH_CACHE and making an asterisk the
only valid parameter value if you use that qualifier (but asterisk is
invalid for every other SET VOLUME qualifier):
$ SET VOLUME * /FLUSH_CACHE
I think this is less elegant than the proposed new FLUSH command.
This command doesn't invalidate the contents of the cache by the way. It
merely writes to disk the data in the cache that has not yet been written to
disk (writes that have been delayed because they make use of VDC's
write-behind caching feature). It doesn't invalidate any data in any
caches in the cluster.
Judy
|
| Oh, it wasn't clear in .0 that you were talking about a
command line interface that you won't be supporting with your
V1.0 product.
As for no other SET VOLUME qualifier taking an asterisk, I don't
know of any other OpenVMS file-system command that applies to
all mounted volumes. We are visiting new ground here. SET VOLUME
is a singular command, ie, it works on only one volume at a time.
Otherise, it would be SET VOLUMES, right? :-) SET VOLUME (and
likewise SET DEVICE, MOUNT, etc.) do work across multiple nodes
in a cluster, but always on a single volume, etc.
For system-wide (ie device-wide) commands, traditionally those
are attached to SET or MCR SYSMAN. Perhaps a SET DATA_CACHE/FLUSH?
Using FLUSH as a top-level command limits you later when you want to
do something to the data cache that isn't a flush. Perhaps latter
on, you want to allow a system manager to control the size, the
amount per volume, the rate at which it is throttled back to the
physical disk, etc.
-John
|