Upgrading TimeZone error ORA-56920: a prepare or upgrade window or an on-demand or datapump-job loading

when you upgrade your database, there are post-upgrade actions….among them is upgrading the “time zone“, the following errors were thrown when i successfully upgraded database from 12cR1 to 18c:

ERROR at line 1:

ORA-56920: a prepare or upgrade window or an on-demand or datapump-job loading of a secondary time zone data file is in an active state

ORA-06512: at “SYS.DBMS_SYS_ERROR”, line 79

ORA-06512: at “SYS.DBMS_DST”, line 1390

ORA-06512: at line 1

Solution:

SQL> ALTER SESSION SET EVENTS ‘30090 TRACE NAME CONTEXT FOREVER, LEVEL 32’;

SQL> exec dbms_dst.unload_secondary;