Hi (again) Tom:
> Do I needed to de-activiate the volume group before I increase the max_pv setting?
No. From the 11.31 manpages (which in this case should apply to 11.23): "...on volume groups version 1.0 that are deactivated or activated in standalone or exclusive mode only. The command will fail on volume groups activated in shared mode." SAince you are running 11.23 your volume groups are version 1.0.
Regards!
...JRF...