The nearest equivalent in AIX is the bosboot command. You need to use this after you have mirrored you rootvg so the system knows there is a mirror of the boot disk. You run bosboot -a after you have done the mirroring. (You will get a message telling you to run bosboot -a if you have mirrored rootvg with the command mirrorvg rootvg.)
You also will be told to change your bootlist. You do this with the bootlist -m normal hdisk0 <newhdisk> cd0 and bootlist -m service hdisk0 <newdisk> cd0, etc.
Likewise, if you break the mirror, you need to run bosboot and bootlist to tell the system that second boot disk isn't there any more.
Look at the man pages for bosboot and bootlist.
I know lvlnboot can be used to create the dumpdevice and the primary swap device. You can do this in AIX through smit.
Does this answer your question? I've done a lot of mirroring of the rootvg (vg00 in HP) and can send you the steps I have used. It is really very easy, but you need to do the bosboot and bootlist commands, and make sure volume group quorum is turned off for the mirroring to be effective.
