Two combine two volume groups into a single volume group, use the vgmerge command. You can merge an inactive "source" volume with an active or an inactive "destination" volume if the physical extent sizes of the volume are equal and the physical and logical volume summaries of both volume groups fit into the destination volume groups limits.

The following command merges the inactive volume group my_vg into the active or inactive volume group databases giving verbose runtime information.

vgmerge -v databases my_vg