An HMC can be deregistered using the “hmc remove” command:

hmc remove [-v] <hmc> ...

The HMC is then removed from the hmc.list file in the user’s home directory. Managed systems and LPARs that were only accessible via this HMC are then also removed from the local files ms.list and lpar.list. HMC and associated managed systems and LPARs can then no longer be administered by the LPAR-Tool.

One or more HMCs must be specified:

$ hmc remove hmc01
$

Afterwards, the HMC is no longer known to the LPAR-Tool:

$ hmc show hmc01
USAGE:
   hmc show [-o <format>] [{-f|-j|-y}] [-F <fields>] [-s <selections>] [<hmc> ...]
ERROR: HMC hmc01 is not known
$

However, the HMC can be re-registered at any time using the hmc add command!