# chvg -g
From the man page:
1. The user might be required to execute varyoffvg and then varyonvg on the
volume group for LVM to see the size change on the disks.
2. There is no support for re-sizing while the volume group is activated in
classic or enhanced concurrent mode.
3. There is no support for re-sizing for the rootvg.
chvg -g datavg1