>ADSM steadfastly refuses to back up a file
>that its database says it already has an exact copy of.

Now, we must remember that there are multiple flavors of ADSM "backup".
Incremental Backup will not make another copy if it already has an
exact image; but Selective Backup "...sends copies of the files to the
server regardless of whether they have changed since the last backup"
(per the Backup-Archive Client manual).  ADSM provides flexibility to
meet various needs.  But has been stressed by many customers on this
list, it can be counterproductive to force ADSM to look like some
other backup scheme that a manager was familiar and comfortable with.
ADSM was developed to provide a better way to do things.  As Apple
Computer says, "Think different".
      Richard Sims, Boston University OIT