First of all, check compatibility solution matrix to see if it is supported online resizing of one LUN with your specific storage and operating system .
(I had problems in the past with a 3PAR which didn't support online resizing with HPUX)
Once LUN resized, kernel must see new disk size check it with:
diskinfo /dev/rdisk/disk###
If not, try to scan and run diskinfo again.
ioscan -fnNCdisk
If no results, try to reboot the server.
If there is no onlineJFS you could see the new disk size but always will need umount that filesystem to extend it.