Is there a way to make the mount point unwritable? I can't write a script or anything to check, but thought there might be a way to do this via permissions. On Linux you could make it immutable. The problem is that a backup process is filling up the root file system when the mount point fails.
Does AIX let you mount a filesystem over an existing filesystem? Under Linux, you could do something like this:
But you can mount something over it like this:
And that filesystem is writable:
If the second mount fails, you're still left with a read-only filesystem. If AIX supports this sort of overlapping mount this might do what you want.