Bill,
I could give you two PMRs opened within the last week dealing with lpars
on different racks.
They will drop when IPLing the entire frame (like when upgrading firmware)
and probably also when IPLing just the lpar.
You must start the shared sessions on the HMC.
It is recommended that you enable the console takeover ability on the lpar
(from a different thread today).
Both PMRs ended with basically working as designed.
Both happened on 7.3.4 SP2 and MH01181.
Console Takeover and Recovery
http://publib.boulder.ibm.com/infocenter/iseries/v6r1m0/topic/rzajr/rzajrconsoletakeoverandrecover.htm
I've suggested that they update this to also include HMC.
Rob Berendt