change the primary dump device of a vio server

UNIX AIX
1

Hi
how to change the primary dump device in a vio server ?

 
$ ioslevel
2.2.0.11-FP-24 SP-01
$ oem_setup_env
# sysdumpdev -l
primary              /dev/sysdumpnull
secondary            /dev/hd6
copy directory       /var/adm/ras
forced copy flag     TRUE
always allow dump    TRUE
dump compression     ON
type of dump         traditional
2 
sysdumpdev -P -p'/dev/blubb'