Use IBM's Microcode Discovery Service at the following URL to determine what microcode should be updated, to retrieve the microcode, and the instructions for installing the microcode.
Normally the "java applet" is used to peform the microcode discovery which requires the password for the user "invscout" to be set. This also requires internet communication from the system over port 808. To use the java applet perform the following steps on the target system:
pwdadm -c invscout
lsattr -El sys0 -a modelname -F value
lsattr -El sys0 -a systemid -F value
Use the facilities built into the HMC for performing microcode updates to all managed systems.