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The Question is:
Changes to data in file mapped global sections are lost upon power failure
unless flushed implicitly by OpenVMS (as part of paging) or explicitly by the
application. A better solution would be if OpenVMS could perform an automatic
shutdown on power failur
e sustained by a little say 120 sec. internal battery. Does such a feature exist?
The Answer is :
The basic approach with the global sections can unfortunately have
some potential flaws, as one obvious potential exposure here is to
system failures and to application failures -- or worse, to failures
which can leave potentially corrupted data in the sections resulting
from an aberant application failure. Galactic memory is particularly
vulnerable -- not because of the operation across multiple instances
in an OpenVMS Galaxy configuration -- because it is the only type of
global section that can typically survive even an OpenVMS system
failure with its contents entirely intact.
Put another way, this area is where available middleware and related
approaches can provide benefit and value -- with the information written
to static storage (eg: disk) and/or replicated across multiple servers
(eg: Compaq RTR, or the Iona or BEA middleware offerings), your
application can then restart. And you don't have to write and
maintain this code.
Also please see existing discussions including topics (6960), (4487),
(4051), (3791), (3635), (3365), (2486), (2637), (2181), (860), and
others -- these are discussions that can be relevent to correct
operations of shared memory on OpenVMS.
That said, the failure modes of the shared memory section can be
seperated from the discussions of standby power, battery backup, and
controlled shutdown.
The OpenVMS Wizard is aware of no current Alpha systems that offer
internally-integrated battery backup, this capability is assumed to
be provided external to the system via UPS, motor generator, or similar.
(In addition to the power requirements of the system, there are a large
number of other supporting components of the local computing environment
that can require standby power -- most notably, storage controllers,
storage shelves, display consoles, and network hardware.)
Please see the OpenVMS FAQ for pointers to information on available
UPS control software.
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