The AIX kernel is available in 32-bit or 64-bit mode. If a 32-bit kernel is running and you want to switch to 64-bit kernel , use the following command. ( provided the system has the “bos.mp64” file set installed. )
# ln –sf /usr/lib/boot/unix_64 /unix
# ln –sf /usr/lib/boot/unix_64 /usr/lib/boot/unix
# bosboot –ak /usr/lib/boot/unix_64
# shutdown –Fr