I've been on hand when lot's of bears have been killed and never saw or ever heard about the need to have a back-up weapon for black bears.I suppose if the almost impossible incident happened where a wounded black bear turned on you and attacked,you could always drop the 30-06 anduse the 9mm to put yourself out of your misery.

If a bear did in fact attack,and you emptied your rifle,you'd be history by the time you had a chance to respond with a handgun.A 9mm is totaly inadequate to use asa back-up weapon for bear.