VIOS 3.1.1 - Increase # of NPIV’s per FC port to 255?


I noticed that starting with VIOS 3.1.1, there is meant to be an increased number of NPIVs per FC port i.e. increase from 64 to 255.


"An increased number of NPIVs allowed per Fibre Channel port on the 32 GB Fibre Channel HBA. The current limit is 64, and more NPIVs per port will provide better utilization, density, and efficiency."


I was left wondering if this increase is expected to be available without configuration or not?


Looking at my VIOS system, lsnports still reported 64 and not 255. However, I'm using 16GB FC adapters not 32GB.


$ ioslevel


$ lsnports

name             physloc                        fabric tports aports swwpns  awwpns

fcs0             U78C9.001.WZS00BP-P1-C12-T1         1     64     62   3088    3080

fcs1             U78C9.001.WZS00BP-P1-C12-T2         1     64     61   3088    3077

fcs2             U78C9.001.WZS00BP-P1-C6-T1          1     64     64   3088    3086

fcs3             U78C9.001.WZS00BP-P1-C6-T2          1     64     64   3088    3086


In the past, on older VIOS versions, I was aware of an (unsupported) way to increase this value that required us to modify a "hidden" ODM attribute, max_npivs i.e.


$ oem_setup_env

# chdev -l fcs0 -a max_npivs=128-P

fcs0 changed


# exit

$ shutdown -restart


After reboot:


$ lsnports

name             physloc                        fabric tports aports swwpns  awwpns

fcs0             U2C4E.001.DBJ8765-P2-C5-T1          1    128    127   2048    2045

fcs1             U2C4E.001.DBJ8765-P2-C5-T2          0     64     64   2048    2048


In talking with the development support team I was informed that the default max value for max_npivs is still 64, for compliance with older supported HBAs (NPIV capable).


#define DEFAULT_MAX_NPIVS      64


And, when you use 16 Gbps or lesser adapters, the maximum limit of 64 still applies. To enable the new maximum value for a 32Gbps adapter, the below action is required:



$ chdev -dev fcs# -perm -attr max_npivs=255

$ shutdown -restart


This change is supported with 32 Gbps FC adapters. Above action are not dependent on VIOS level 2.2.6.x or 3.1.x.


Note that there is also a known defect 1074787 LSNPORTS TPORTS VALUE MAY CHANGE UNEXPECTEDLY ON VIOS.


APAR IJ12857 72M (

APAR IJ12914 72Q (  

APAR IJ12861 61r (



Related: Maximum value for num_cmd_elems on AIX/VIOS