"Opening Database <DBNAME> in upgrade mode failed" during AutoUpgrade
I'm performing an Oracle upgrade from 12.1.0.2 to 19 (including a server move) on Windows. On the target server I have started autoupgrade and am getting an error "Opening Database <DBNAME> in upgrade mode failed".
When I try to connect to the database using "sqlplus / as sysdba" (under a domain user in the local ORA_DBA group) I get a "ORA-12638: Credential retrieval failed" error. I see the AutoUpgrade has created a new Windows service called "AutoUpgradeOracleService<SID>" (which is running instead of the usual OracleService<SID>) and this new service is running as a Local System account. If I change it do run as my domain Oracle Home user account and restart it, then the error from "sqlplus / as sysdba" goes away and I am able to successfully start the database in upgrade mode. However