Vary-on process

The vary-on process is one of the mechanisms that the LVM uses to ensure that a volume group is ready to use and contains the most up-to-date data.

The varyonvg and varyoffvg commands activate or deactivate (make available or unavailable for use) a volume group that you have defined to the system. The volume group must be varied on before the system can access it. During the vary-on process, the LVM reads management data from the physical volumes defined in the volume group. This management data, which includes a volume group descriptor area (VGDA) and a volume group status area (VGSA), is stored on each physical volume of the volume group.

The VGDA contains information that describes the mapping of physical partitions to logical partitions for each logical volume in the volume group, as well as other vital information, including a time stamp. The VGSA contains information such as which physical partitions are stale and which physical volumes are missing (that is, not available or active) when a vary-on operation is attempted on a volume group.

If the vary-on operation cannot access one or more of the physical volumes defined in the volume group, the command displays the names of all physical volumes defined for that volume group and their status. This helps you decide whether to vary-off this volume group.