CHANGING Normal VG TO Big VG & Big VG TO Scalable VG

CHANGING Normal VG TO Big VG & Big VG TO Scalable VG

Changing Normal VG to Big VG:

If you reached the MAX PV limit of a Normal VG and playing with the factor (chvg -t) is not possible anymore you can convert it to Big VG.
It is an online activity, but there must be free PPs on each physical volume, because VGDA will be expanded on all disks:

root@bb_lpar: / # lsvg -p bbvg
bbvg:
PV_NAME           PV STATE          TOTAL PPs   FREE PPs    FREE DISTRIBUTION
hdisk2            active            511         2           02..00..00..00..00
hdisk3            active            511         23          00..00..00..00..23
hdisk4            active            1023        0           00..00..00..00..00

root@bb_lpar: / # chvg -B bbvg
0516-1214 chvg: Not enough free physical partitions exist on hdisk4 for the
        expansion of the volume group descriptor area.  Migrate/reorganize to free up
        2 partitions and run chvg again.

In this case we have to migrate 2 PPs from hdisk4 to hdsik3 (so 2 PPs will be freed up on hdisk4):

root@bb_lpar: / # lspv -M hdisk4
hdisk4:1        bblv:920
hdisk4:2        bblv:921
hdisk4:3        bblv:922
hdisk4:4        bblv:923
hdisk4:5        bblv:924
...

root@bb_lpar: / # lspv -M hdisk3
hdisk3:484      bblv:3040
hdisk3:485      bblv:3041
hdisk3:486      bblv:3042
hdisk3:487      bblv:1
hdisk3:488      bblv:2
hdisk3:489-511

root@bb_lpar: / # migratelp bblv/920 hdisk3/489
root@bb_lpar: / # migratelp bblv/921 hdisk3/490

root@bb_lpar: / # lsvg -p bbvg
bbvg:
PV_NAME           PV STATE          TOTAL PPs   FREE PPs    FREE DISTRIBUTION
hdisk2            active            511         2           02..00..00..00..00
hdisk3            active            511         21          00..00..00..00..21
hdisk4            active            1023        2           02..00..00..00..00

If we try again changing to Big VG, now it is successful:
root@bb_lpar: / # chvg -B bbvg
0516-1216 chvg: Physical partitions are being migrated for volume group
        descriptor area expansion.  Please wait.
0516-1164 chvg: Volume group bbvg2 changed.  With given characteristics bbvg2
        can include up to 128 physical volumes with 1016 physical partitions each.

If you check again, freed up PPs has been used:
root@bb_lpar: / # lsvg -p bbvg
bbvg:
PV_NAME           PV STATE          TOTAL PPs   FREE PPs    FREE DISTRIBUTION
hdisk2            active            509         0           00..00..00..00..00
hdisk3            active            509         17          00..00..00..00..17
hdisk4            active            1021        0           00..00..00..00..00

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Changing Normal (or Big) VG to Scalable VG:

If you reached the MAX PV limit of a Normal or a Big VG and playing with the factor (chvg -t) is not possible anymore you can convert that VG to Scalable VG. A Scalable VG allows a maximum of 1024 PVs and 4096 LVs and a very big advantage that the maximum number of PPs applies to the entire VG and is no longer defined on a per disk basis.

!!!Converting to Scalable VG is an offline activity (varyoffvg), and there must be free PPs on each physical volume, because VGDA will be expanded on all disks.

root@bb_lpar: / # chvg -G bbvg
0516-1707 chvg: The volume group must be varied off during conversion to
        scalable volume group format.

root@bb_lpar: / # varyoffvg bbvg
root@bb_lpar: / # chvg -G bbvg
0516-1214 chvg: Not enough free physical partitions exist on hdisk2 for the
        expansion of the volume group descriptor area.  Migrate/reorganize to free up
        18 partitions and run chvg again.


After migrating some lps to free up required PPs (in this case it was 18), then changing to Scalable VG is successful:
root@bb_lpar: / # chvg -G bbvg
0516-1224 chvg: WARNING, once this operation is completed, volume group bbvg
        cannot be imported into AIX 5.2 or lower versions. Continue (y/n) ?
...
0516-1712 chvg: Volume group bbvg changed.  bbvg can include up to 1024 physical volumes with 2097152 total physical partitions in the volume group.