https://www.ibm.com/support/pages/when-using-hmc-gui-you-see-message-unable-connect-database-error-occurred

First step is to clone the OS:

• Using hardware clone on storage array
• Using software cloning on VIOS: alt_disk_copy -d hdiskx

Then once the cloned disk is assign to the second VIOS, start it and

# stopsrc -g rsct_rm; stopsrc -g rsct

# chdev -l cluster0 -a node_uuid=00000000-0000-0000-0000-000000000000

Or

# odmdelete -o CuAt -q 'attibute=node_uuid'

Now generate a new node ID

# /usr/sbin/rsct/bin/mknodeid -f

# lsattr -El cluster0
# /usr/sbin/rsct/bin/lsnodeid
# /usr/sbin/rsct/install/bin/recfgct

# lspartition -dlpar
# lssrc -g rsct_rm; lssrc -g rsct
# startsrc -s ctcas

https://public.dhe.ibm.com/systems/virtualization/vio/ztools/CMDB/

Now best is to reboot