If the jfslog has been damaged for any reason, it will cause the filesystems to not be mounted. Assume the filesystem /dataVolumes/proof7.2.0 fails to mount and fsck does not help. Find out the name of the jfslog that belongs to this filesystem:
# lsvg -l svg2
svg2: LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT slv2.0 jfs 1080 1080 2 open/syncd /dataVolumes/proof7.2.0 loglv02 jfslog 1 1 1 open/syncd N/A
we will reformat the jfslog. Enter:
1.all filesystems associated with the jfslog *must* be unmounted prior to running logform !
2. logform /dev/loglv02
This command will ask the horrible question "Do you wish to destroy the log?". Just say yes. This will get you a new, clean jfslog. Then we'll run fsck on this filesystem to ensure it's back.