In this example, we will increase the /opt size from 8160M to 9024M

Check the initial size with bdf command:

gz@hpux:/opt#bdf .
Filesystem          kbytes    used   avail %used Mounted on
/dev/vg00/lvol6    8355840 6828584 1515352   82% /opt

As you can see, the filesystem is part of lvol6 logical volume and vg00 volume group. Let's see if we have free physical extends free on the volume:

gz@hpux:/opt#vgdisplay
--- Volume groups ---
VG Name                     /dev/vg00
VG Write Access             read/write
VG Status                   available
Max LV                      255
Cur LV                      14
Open LV                     14
Max PV                      16
Cur PV                      1
Act PV                      1
Max PE per PV               4384
VGDA                        2
PE Size (Mbytes)            32
Total PE                    4343
Alloc PE                    3295
[color=green]Free PE                     1048[/color]
Total PVG                   0
Total Spare PVs             0
Total Spare PVs in use      0
VG Version                  1.0
VG Max Size                 2192g
VG Max Extents              70144

So, we have enough for our operation and we proceed.
We increase first the logical volume with lvextend command:

gz@hpux:/opt#lvextend -L 9000 /dev/vg00/lvol6
Warning: rounding up logical volume size to extent boundary at size [color=red]"9024" MB[/color].
Logical volume "/dev/vg00/lvol6" has been successfully extended.
Volume Group configuration for /dev/vg00 has been saved in /etc/lvmconf/vg00.conf

Now we resize the filesystem to the logical volume's size with fsadm command:

gz@hpux:/opt#fsadm -F vxfs -b 9024M /opt
vxfs fsadm: V-3-23585: /dev/vg00/rlvol6 is currently 9216000 sectors - size will be increased

And this is the final result:

gz@hpux:/opt#bdf .
Filesystem          kbytes    used   avail %used Mounted on
/dev/vg00/lvol6    9240576 6828624 2393136   74% /opt