SIMPLE_INTEGER is a predefined subtype of the PLS_INTEGER data type that has the same range as PLS_INTEGER and has a NOT NULL constraint.
It differs from PLS_INTEGER in its overflow semantics.
If you know that a variable will never have the value NULL or need overflow checking, declare it as SIMPLE_INTEGER rather than PLS_INTEGER.
Without the overhead of checking for nullness and overflow, SIMPLE_INTEGER performs significantly better than PLS_INTEGER.
If and only if all operands in an expression have the data type SIMPLE_INTEGER, PL/SQL uses two's complement arithmetic and ignores overflows.
Values can wrap from positive to negative or from negative to positive; for example:
SQL> SQL> DECLARE-- from www . j av a2 s . c om 2 n SIMPLE_INTEGER := 2147483645; 3 BEGIN 4 FOR j IN 1..4 LOOP 5 n := n + 1; 6 DBMS_OUTPUT.PUT_LINE(TO_CHAR(n, 'S9999999999')); 7 END LOOP; 8 FOR j IN 1..4 LOOP 9 n := n - 1; 10 DBMS_OUTPUT.PUT_LINE(TO_CHAR(n, 'S9999999999')); 11 END LOOP; 12 END; 13 / +2147483646 +2147483647 -2147483648 -2147483647 -2147483648 +2147483647 +2147483646 +2147483645 PL/SQL procedure successfully completed. SQL>