I have an Oracle DataGuard envrionment that it has been upgraded from 12.1.0.2 to 18C recently. After the upgrade, the ODG broker gave the following error: ORA-1005: null password given; logon denied

DGMGRL> show configuration;          

Configuration - DG_APROD

  Protection Mode: MaxPerformance
  Members:
  DB1 - Primary database
    Error: ORA-1005: null password given; logon denied

    DB2- Physical standby database 

Fast-Start Failover: DISABLED

Configuration Status:
ERROR   (status updated 0 seconds ago)

It was because the oracle password was missing after the upgrade from the new $ORACLE_HOME/dbs. After I copied it over, the broker detected it automatically and showed:

GMGRL> show configuration

Configuration - DG_APROD

  Protection Mode: MaxPerformance
  Members:
  DB1 - Primary database
    DB2 - Physical standby database 
      Error: ORA-16599: Oracle Data Guard broker detected a stale configuration

Fast-Start Failover: DISABLED

Configuration Status:
ERROR   (status updated 124 seconds ago)

ORA-16599 usually is just a transient error. It will go away after a few minutes. If not, you can try to disable/enable the configuration or re-create the configuration.

• Oracle