Good post by Adrian Mahendrata (thank you)
Growing the LUN size on AIX is very simple and can be done online
What happens when you need to add more space to your volume group? Well, you could assign a new Logical Unit Number (LUN) from your Storage Area Network (SAN) and add the LUN to the volume group. But because the AIX Logical Partition (LPAR) is running on SAN storage, why not just expand the LUN and get AIX to recognize the new LUN size?
Read on here