Unable to increase MaxLPs for LV

As part of growing filesystems on AIX, you often hit the message:

Error Message:  0516-787 extendlv: Maximum allocation for logical volume is 512

which is a bit of a legacy setting from the days of small disks and when you could not shrink filesystems.

This is easily over-come by running chlv -x <number> but I was recently thwarted by being met by another error from trying this fairly routine command:

# chlv -x 65536 data2_lv
0516-1389 chlv: The -x parameter for MaxLPs must be between 1 and 32768.
        It cannot be smaller than the existing number of LP's.

It turns out that “MAX PPs per VG” limits the “MaxLPs” setting.

# lsvg data2_vg
VOLUME GROUP:       data2_vg                 VG IDENTIFIER:  00c85c6700004c000000015c5d99c816
VG STATE:           active                   PP SIZE:        128 megabyte(s)
VG PERMISSION:      read/write               TOTAL PPs:      31992 (4094976 megabytes)
MAX LVs:            256                      FREE PPs:       0 (0 megabytes)
LVs:                1                        USED PPs:       31992 (4094976 megabytes)
OPEN LVs:           1                        QUORUM:         5 (Enabled)
TOTAL PVs:          8                        VG DESCRIPTORS: 8
STALE PVs:          0                        STALE PPs:      0
ACTIVE PVs:         8                        AUTO ON:        yes
MAX PPs per VG:     32768                    MAX PVs:        1024

To fix this, run chvg -P 64K <VGname> which will set “MAX PPs per VG” to 65536.