Change automatic database field after a certain time

Procedure is the solution to your problem.

Develop your Store Procedure:

Syntax error:

    CREATE [OR REPLACE] PROCEDURE procedure_nome
      [ (parameter [,parameter]) ]
  IS
      [declaration_section]
  BEGIN
      executable_section
  [EXCEPTION
      exception_section]
  END [procedure_nome];

Example of how it would apply to the problem:

    CREATE OR REPLACE Procedure AtualizaStatusVisitante

  BEGIN

   UPDATE visitante SET vistiante_status = 'Ausente' WHERE vistiante_status = 'Pendente';

  COMMIT;

  EXCEPTION
  WHEN OTHERS THEN
     raise_application_error(-20001, 'Ocorreu um erro');
  END;

In this example, it performs an UPDATE when the visitor is with STATUS = Pendente

With the procedure created time to apply a schedule, for this will be used JOBs that allows to create this type of activity.

begin
  sys.dbms_job.submit(job => :job,
                      what => 'begin PRC_sua_rotina; end;',
                      next_date => to_date('26-01-2018 20:41:52', 'dd-mm-yyyy hh24:mi:ss'),
                      interval => 'TRUNC(sysdate+1) + 1/24*4');
  commit;
end;

Only change NEXT DATE to the date you want to run the FIRST time. Then, this date will be automatically updated to the date of that "interval", that is, the next day + 4 hours.

Sources:

Here1

Here2

Here3