I had trouble to create a system trigger. The following is how that happened.

SQL> create or replace trigger sys_test
2 after logon on sys
3 begin
4 null;
5 end;
6 /
after logon on sys
*
ERROR at line 2:
ORA-30506: system triggers cannot be based on tables or views.

By following Oracle documentation, I have run the scripts dbmsstdx.sql and catproc.sql in advance.

Thanks for any help.