That's right. Security is an issue, but so are the file types.
UNIX has stream file types, and VMS has RMS-indexed, sequential
and directory structures, too. VMS supports file version numbers,
which UNIX interprets as something else. Proxy mappings between
UNIX/VMS file owners have to be one-to-one. Several VMS/UCX NFS
mount/ qualifiers have to be mentioned, including /CONVERSION
and /SERVER=UNIX to specify VMS/UNIX conversion for a VMS NFS client.
The reason VMS files won't execute on a UNIX NFS mount is obvious.
DCL commands are not found in UNIX verb tables, and vice-versa.
NFS is no good for backups either, since ownership is lost. That
would be another excellent implementation for the VMS BACKUP utility.
We're using UNIX rdump to VMS rmt server, triggered by TCP sockets.
So, UNIX/VMS NFS applications are limited to sequential file storage
I haven't had any experience with VMS<->UNIX NFS implementations,
but I haven't had any problems with multivendor UNIX NSF
implementations. The primary problem with going between UNIX
and VMS (or DOS or OS/2) is going to be that the security
methods on the filesystems are different (or nonexistent).
"Wonder is the foundation of all philosophy, inquiry the
progress, ignorance the end." (Montaigne)