How can I directly read out the VGDA of a PV (hdisk)? :

Information about VGx, LVx, filesystems, etc. are stored in the ODM. But these information are also written to the VGDA of the disks itself. You can read the information directly from the disk's VGDA with a command like this:

 # lqueryvg -Atp hdisk100

You can use

 # redefinevg -d hdisk100 myvg

to synchronize the ODM with the information of the VGDA. You can also synchronize the VGDA with the information stored in the ODM:

 # synclvodm myvg