[Info-vax] Reloading device drivers on x86-64 VMS

[Craig A. Berry]

On 3/8/15 8:38 PM, David Froble wrote:

> If you want to install a new version of a sharable image, if it's
> compatible with the old version, what does it matter how long before the
> old version isn't used?  If it isn't compatible, I think you got more to
> worry about than replacing a sharable image.

I never said anything about loading a new version. The word was "unload"
and in a subsequent post I referenced "a dlclose() or equivalent that
actually frees up resources," which, despite the reference provided,
seems not to have gotten the point across.

Let me try again with an example. A modern web framework might have some
dozens of modules or classes or extensions or plug-ins or assemblies or
whatever the loadable pieces are called in your language of choice, and
each might involve loading one or two or ten shareable images (or more,
given the long dependency chains). A web server process might load up
one set of these things to satisfy one request, but then need to load an
entirely different set to satisfy the next request within the same
process and main image activation, so you end up with all of the
resources required by both sets allocated at the same time. Under some
(but not all) circumstances, it might be desirable to be able to unload
one set before loading another, basically undoing everything that was
done by LIB$FIND_IMAGE_SYMBOL.

Which, as hb said, the VMS image activator cannot do. Which I knew,
which is why I said it might be a nice feature to add, given that other
OS's, such as Linux, already have it (the latter of which I didn't say
previously, but seemed obvious in context).