-- Oracle 11g Simple_Integer
-- The variable declared as SIMPLE_INTEGER has to initialized with 
-- non-null value.  It is a predefined subtype of PLS_INTEGER with 
-- the same range of (-2,147,483,648 to 2,147,483,647) with a 
-- built-in NOT NULL constraint.  It performs better than 
-- PLS_INTEGER as shown in the example below.

-- If declared without a value (NULL), it results in PLS-00218 
-- error (refer output - PLS_00218 Error)

DECLARE 
 v_num   NUMBER := 0;
 v_max   NUMBER := 10000000;

 v_pls   PLS_INTEGER := 0;
 v_start PLS_INTEGER;     -- cannot declare as SIMPLE_INTEGER
 v_end   PLS_INTEGER;

 v_si    SIMPLE_INTEGER := 0;

BEGIN
  v_start := dbms_utility.get_time;
  dbms_output.put_line('-- NUMBER -----------');
  dbms_output.put('Start Time  -> ' ||TO_CHAR(v_start));
  FOR idx IN 1..v_max LOOP
    v_num := v_num+idx;
  END LOOP;
  v_end := dbms_utility.get_time;
  dbms_output.put(' End Time    -> ' ||TO_CHAR(v_end));
  dbms_output.put_line(' Time Lapsed -> ' ||TO_CHAR(v_end-v_start));

  dbms_output.put_line('-- PLS_INTEGER ------');
  v_start := dbms_utility.get_time;
  dbms_output.put('Start Time  -> ' ||TO_CHAR(v_start));
  FOR idx IN 1..v_max LOOP
    v_pls := v_pls+1;
  END LOOP;
  v_end := dbms_utility.get_time;
  dbms_output.put(' End Time    -> ' ||TO_CHAR(v_end));
  dbms_output.put_line(' Time Lapsed -> ' ||TO_CHAR(v_end-v_start));

  dbms_output.put_line('-- SIMPLE_INTEGER ---');
  v_start := dbms_utility.get_time;
  dbms_output.put('Start Time  -> ' ||TO_CHAR(v_start));
  FOR idx IN 1..v_max LOOP
    v_si := v_si+1;
  END LOOP;
  v_end := dbms_utility.get_time;
  dbms_output.put(' End Time    -> ' ||TO_CHAR(v_end));
  dbms_output.put_line(' Time Lapsed -> ' ||TO_CHAR(v_end-v_start));
END;
/

Number, PLS_Integer, Simple_Integer Analysis