Restricting root logins?

[JJDAVIS at cc.utah.edu]

I'd like to restrict root logins on our 530 to the console.
On a Sun system, I'd edit the /etc/ttytab:

console	"/usr/etc/getty std.9600"	sun	off	secure
ttyp0	none				network	off
 .
 .
 .

How do I get this effect in AIX (3.1, July updates)?