I'm curious if Tivoli support gave you any idea of what TYPE of corruption
this error message indicates, and what they said about the DB mirror.  With
MIRRORWRITEDB=SEQUENTIAL, you could (at least in theory) have had corruption
in the primary copy, but not the mirror copy.  (Or maybe TSM doesn't issue
the message until it has tried both copies already?)

I would have tried to remove the primary copy of the DB from the
configuration, and come up with just the mirror, just to see if the result
was any different...