there are a few ways to fix this problem

1. Fix the odm view of the root
========================
if you can run this command it try this prosedure
lqueryvg -Atp hdisk0
redefinevg -d hdisk0 rootvg
synclvodm -v rootvg


If one did not work try this one
============================
2. Make a backup of the ODM databsess be for you start
==========================================
Part1 Backup you ODM
1. cd /etc/objrepos
2. mkdir bak
3. cp Cu* bak

Part2 --> Run this script
#!/bin/ksh
PV=/dev/ipldevice
VG=rootvg
lqueryvg -Lp $PV | awk '{ print $2 }' | while read LVname; do
odmdelete -q "name = $LVname" -o CuAt
odmdelete -q "name = $LVname" -o CuDv
odmdelete -q "value3 = $LVname" -o CuDvDr
odmdelete -q "dependency = $LVname" -o CuDep
done
odmdelete -q "name = $VG" -o CuAt
odmdelete -q "parent = $VG" -o CuDv
odmdelete -q "name = $VG" -o CuDv
odmdelete -q "name = $VG" -o CuDep
odmdelete -q "dependency = $VG" -o CuDep
if [ "$VG" = rootvg ]
then
odmdelete -q "value1 = 10" -o CuDvDr
else
odmdelete -q "value1 = $VG" -o CuDvDr
fi
odmdelete -q "value3 = $VG" -o CuDvDr
importvg -y $VG $PV # ignore varyoffvg errors
varyonvg $VG
synclvodm -Pv $VG
savebase

DO a lspv to see if you have a rootvg if not use the backout plan

PART3 Backout
1. cd /etc/objrepos/bak
2. cp Cu* /etc/objrepos/



========================================================
Last hope
=======
3. Mksysb restore of the last mksysb you have taken (last resort)



Before you do any of this you may just want to check with IBM support On your problem
Start at the top prosedure firs and work your way down as 2 and 3 are more
disruptive prosedures as soon as the problem is fixed let me know wich one you used in the end.