[Info-vax] Request description of UFS for VMS person

[Bob Koehler]

In article <33c33267-2172-433d-9a98-fdd1b9cbda3b at y7g2000yqa.googlegroups.com>, AEF <spamsink2001 at yahoo.com> writes:
> 
> Then there's the mysterious VMS deletion process which I'd love to
> learn. I only know about it from the strange ANAL/DISK errors about
> file headers being busy, deleted, quasi-deleted, or whatever. I'd love
> to learn about that too.

   This is an area in which every file system I've studied operates the
   same.  There is no file delete primitive at the lowest levels of
   the VMS or UNIX kernel, and I think not Windows, MS-DOS, or classis
   MacOS, either.

   To delete a file the atomic operations are:  open the file, set the
   delete-on-close flag, and close the file.

   Every OS has problems if you try to delete a file that something else
   has open as that last step can't complete until all things close the
   file.  How this is dealt with varies, somehow the OS has to keep
   track that the file is really there and somehow provide a way to
   finish the delete.  The actual last close may not happen until system
   shutdown, and in VMS sometimes it actually just doesn't happen during
   system shutdown.  It is possible to always clean up during boot or
   mount, but on VMS you get to do it manually at your convinience.

   I generally have the automated backup scripts rebuilt the bitmap
   once a week before doing full backups and I find the delete in
   progress files so rare that unless I'm doing a product install I
   do it manually every other month or so.