Meanwhile I found a solution for the topic mentioned. But I would like to let others know how I did that.
I found this great description from a guy whose name is "Ryan".
see: Ryan's AIX description
The only thing I had to change was: use jfs instead of jfs2 (for whatever reason).
Here is a summary of the commands I used to get this working:
1. mkvg -y homevg hdisk1 # create a new volume group on the new/free harddisk
2. mklv -t jfslog -y loghomevg homevg 1 # prepare log for the new filesystem
3. mklv -t jfs -y homelv homevg 64G # prepare a 64G partition for the new /home
4. mkfs -o log=/dev/loghomevg -V jfs /dev/homelv # create new jfs filesystem.
5. mkdir /home2 # create a mountpoint for the new filesystem
6. chown bin:bin /home2 # set ownership according to /home
7. mount -o log=/dev/loghomevg /dev/homelv /home2 # mount the new filesystem
Note: in (4) you have to answer with "Yes". Afterwards it will take a while to complete.
After all that I copied the original content of the /home directory to /home2. I did so by using gnu tar, but other approaches should also work:
gtar -cvpf - * | gtar -C /home2 -xpf -
you are done now!
finally you could unmount /home and use /home2 as the new /home directory, e.g. by modifying /etc/filesystems appropriately. Alternatively you could assign a new home directory to the users defined in /etc/passwd, e.g. use /home2/buildsys instead of /home/buildsys