Oracle DB Upgrade to 18c fails with Error : ORA-04063: SYS.ALERT_QUE has errors

Problem
DB Upgrade from 11.2.0.4 to 18c failed with ORA-04063: SYS.ALERT_QUE has errors

Solution
SYS.ALERT_QUE corrupted in source database. recreate  SYS.ALERT_QUE  will sort the problem

1. Connect as sysdba and enable restricted mode

  sqlplus / as sysdba
  SQL> alter system enable restricted session;

2. Drop Existing ALERT_QT tables

exec dbms_aqadm.drop_queue_table('ALERT_QT',true);

3.  Re-create tables, sequence, type and queue for server alert

SQL> @$ORACLE_HOME/rdbms/admin/dbmsslrt.sql
SQL> @$ORACLE_HOME/rdbms/admin/catalrt.sql
SQL> @$ORACLE_HOME/rdbms/admin/catmwin.sql
SQL> @$ORACLE_HOME/rdbms/admin/exechae.sql

4. Compile Invalid objects

SQL> @$ORACLE_HOME/rdbms/admin/utlrp.sql

5. disable restricted mode

SQL> alter system disable restricted session;

6. Retry the DB upgrade

Reference - Upgrade to 12.2 fails with Error : ORA-04063: SYS.ALERT_QUE has errors (Doc ID 2632809.1)