Tracy ponders:
> Would it have been possible to mount an MPE/V file
> system on an MPE/XL machine as a User/Private Volume?

Nothing like this was ever done that I know of.  With a lot of work it might
have been possible to mount an MPE/V PV in read-only mode.  Updating would
probably have required implementing the entire MPE/V file system in parallel
with the MPE/XL version, since the MPE/V structures lacked places to put all
the information that MPE/XL would have needed, transaction management, etc.

It's hard to imagine this feature being worth the effort in my opinion.
Also MPE/V PVs were a pain in the neck and had performance issues and so
were not commonly used by most customers.  MPE/XL and /iX's "User Volumes"
look similar to MPE/V's "Private Volumes" but the implementation is
completely integrated into the system from the beginning, unlike PVs which
were more of a bolt-on afterthought.

Even today some customers avoid using User Volumes because of all the
problems with Private Volumes.  This is a mistake as User Volumes are a Good
Thing(tm) and *all* production systems should be using them for their
performance and recoverability advantages.

G.

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