AIX LPAR: Increase or Decrease a file system JFS2

{root_lpar5} / # lspv doshvg
0516-306 : Unable to find  doshvg in the Device
        Configuration Database.
{root_lpar5} / # lsvg doshvg
VOLUME GROUP:       doshvg                   VG IDENTIFIER:  00fdc1c900004c0000000133646778de
VG STATE:           active                   PP SIZE:        4 megabyte(s)
VG PERMISSION:      read/write               TOTAL PPs:      1533 (6132 megabytes)
MAX LVs:            256                      FREE PPs:       1276 (5104 megabytes)
LVs:                2                        USED PPs:       257 (1028 megabytes)
OPEN LVs:           2                        QUORUM:         2 (Enabled)
TOTAL PVs:          3                        VG DESCRIPTORS: 3
STALE PVs:          0                        STALE PPs:      0
ACTIVE PVs:         3                        AUTO ON:        yes
MAX PPs per VG:     32512
MAX PPs per PV:     1016                     MAX PVs:        32
LTG size (Dynamic): 256 kilobyte(s)          AUTO SYNC:      no
HOT SPARE:          no                       BB POLICY:      relocatable
{root_lpar5} / # df -m /devilla
Filesystem    MB blocks      Free %Used    Iused %Iused Mounted on
/dev/fslv00     1024.00   1023.52    1%        5     1% /devilla
{root_lpar5} / # chfs -a size=+1024M /devilla
Filesystem size changed to 4194304
{root_lpar5} / # df -m /devilla
Filesystem    MB blocks      Free %Used    Iused %Iused Mounted on
/dev/fslv00     2048.00   2047.37    1%        5     1% /devilla
{root_lpar5} / # chfs -a size=-1024M /devilla
Filesystem size changed to 2097152
{root_lpar5} / # df -m /devilla
Filesystem    MB blocks      Free %Used    Iused %Iused Mounted on
/dev/fslv00     1024.00   1023.52    1%        5     1% /devilla