The dynamic changing of the attributes of a vNIC backing device is only possible to a limited extent. The changeable attributes are as follows:

• • capacity: the guaranteed capacity of the associated logical SR-IOV port.
  • max_capacity: the maximum capacity of the associated logical SR-IOV port.
  • failover_priority: the failover priority (values between 1 and 100).

Of these attributes, only the attribute failover_priority can be changed dynamically. The other two attributes can only be changed in a profile of the LPAR.

The command for changing attributes is “lpar chvnicbkdev” (change vNIC backing device). The vNIC backing device can be specified in one of 4 ways:

• • the logical port ID of the associated logical port, e.g. 27008004.
  • a unique suffix of the physical location code of the associated logical port, e.g. P1-C6-T1-S4.
  • the adapter ID and physical port ID of the associated physical port, e.g. “2 0“.
  • a unique suffix of the physical location code of the associated physical port, e.g. P1-C6-T1.

Before we make a change, we first list the vNIC backing devices of the LPAR aix22:

$ lpar lsvnic -a aix22
                           FAILOVER                                      PHYS  LOGICAL   CURRENT     MAX   
LPAR_NAME  SLOT  FAILOVER  PRIORITY  ACTV  STATUS       VIOS_NAME  ADAPTER  PORT  PORT      CAPACITY  CAPACITY
aix22      6     Yes       50        1     Operational  ms03-vio1  1        0     27004005  2.0       100.0
aix22      6     Yes       50        0     Operational  ms03-vio2  2        0     27008004  2.0       100.0
$

As an example we change the second vNIC backing device (27008004). We set the failover priority to the value 60 and the capacity (cannot be changed dynamically) to 4%:

$ lpar chvnicbkdev aix22 6 27008004 failover_priority=60 capacity=4
INFO: capacity skipped from DLPAR operation
$

The vNIC backing device to be changed is identified by the slot number of the vNIC adapter and the logical port ID. The command returns the information that the capacity has not been updated dynamically (it can only be changed offline in the profile). The listing of the vNIC backing devices shows that the failover priority has been changed, but the capacity has remained the same:

$ lpar lsvnic -a aix22
                           FAILOVER                                      PHYS  LOGICAL   CURRENT     MAX   
LPAR_NAME  SLOT  FAILOVER  PRIORITY  ACTV  STATUS       VIOS_NAME  ADAPTER  PORT  PORT      CAPACITY  CAPACITY
aix22      6     Yes       50        1     Operational  ms03-vio1  1        0     27004005  2.0       100.0
aix22      6     Yes       60        0     Operational  ms03-vio2  2        0     27008004  2.0       100.0
$

In the current profile of the LPAR, however, the capacity has been changed, so that the next time the LPAR is activated with the changed profile, the capacity will be set to 4%:

$ lpar -p standard lsvnic -a aix22
                           FAILOVER                      PHYS              MAX   
LPAR_NAME  SLOT  FAILOVER  PRIORITY  VIOS_NAME  ADAPTER  PORT  CAPACITY  CAPACITY
aix22      6     Yes       50        ms03-vio1  1        0     2.0       100.0
aix22      6     Yes       60        ms03-vio2  2        0     4.0       100.0
$

Note: The capacity can also be changed indirectly by removing the relevant vNIC backing device and then adding it again with a changed capacity.