ORA-04023 during DBUA upgrade from Oracle 12.2.0.1 to Oracle 19c

During Oracle Upgrade using DBUA from 12 to 19, you got ORA-04023 - Object SYS.DBMS_STANDARD could not be validated or authorized.

There are some causes to this error :

ORACLE_PATH or SQLPATH are set in the user environment;

Oracle Invalid objects and invalid components;

What can I do?

As a first step, check for invalid objects and invalid components with the statements:

 SQL> select comp_name, version, status from dba_registry;
 SQL> select owner, object_name, object_id, object_type, created, last_ddl_time, timestamp, status from dba_objects where status != 'VALID' order by object_name;

Reset ORACLE_PATH (UNIX) or SQLPATH (WINDOWS) environment variable.

I hope this could help!