A database trigger is an alternative for?
I don't expect the writer of the question meant it this way, but words mean things and the question specifies a "database trigger", therefore there is no correct answer.


  A DATABASE trigger is created on the database and fires whenever any database user initiates the triggering event. (PL/SQL Language Reference - DATABASE Triggers)


Unlike Row and Statement triggers, Database triggers fire for things like 
AFTER STARTUP ON DATABASE, AFTER SERVERERROR ON DATABASE and AFTER LOGON ON DATABASE.