Triggers on system events can be defined at the database level or schema level. For example, a database shutdown trigger is defined at the database level: Triggers on DDL statements or logon/logoff events can also be defined at the database level or schema level.NSTEAD OF triggers provide a transparent way of modifying views that cannot be modified directly through DML statements (INSERT, UPDATE, and DELETE). These triggers are called INSTEAD OF triggers because, unlike other types of triggers, Oracle fires the trigger instead of executing the triggering statement.