I suspect I asked this before, but I don't remember... Can I do this?
Close a database, replace it with a fresh slapadded one and reopen
it, _without_ clients seeing its subtree temporarily disappear.
So instead of deleting the database entry, modify it so operations
against it either fail with 'unavailable' or (preferably) wait for the
database to become on-line again, subject to the normal time limits.