meanwhile I found out how to create a bootable DVD .iso image.
# note: I have unmounted /home before creating the iso image. Otherwise I would need multiple DVDs
# note: I have mounted an NFS directory below /volumes/aixsav
# create some needed subdirectories
for i in mksysb_target tmp iso mkcd; do
test -d $extdir/$i || mkdir $extdir/$i || exit 1
# finally: create the .iso image.
/usr/sbin/mkdvd -M $extdir/mksysb_target -C $extdir/tmp -I $extdir/iso -S
This needs some time. But after all I had my image in the iso subdirectory. I went to another machine and burned the image to a DVD (under linux).
For testing I have shut down the AIX machine and replaced the existing harddisk with a another empty one. Then I booted up and followed the onscreen instruction for restoring from DVD.
Everything went fine. Even the Usernames/Passwords, Hostname, IP-Address everything was like on the original harddrive!
a final note: be patient! creating the Image and booting from the DVD will need some time. Just lay back and wait ...