Here are the rules about OUT parameters:

► A formal OUT parameter acts like an un-initialized variable. It must be assigned with new values before the end of the procedure or function.

► An actual OUT parameter must be a variable.

► An actual OUT parameter will not pass any value to the formal parameter.

► An actual OUT parameter will receive a copy of the value from the formal parameter at the end of the procedure or function.

Here is good example of a procedure with an OUT parameter:

SQL> CREATE OR REPLACE PROCEDURE WELCOME AS

2 SITE CHAR(40) := 'rendc.org';

3 MESSAGE CHAR(80);

4 PROCEDURE WELCOME_PRINT(S IN CHAR, M OUT CHAR) AS

5 BEGIN

6 M := 'Welcome to ' || S;

7 END;

8 BEGIN

9 WELCOME_PRINT('MySpace.com', MESSAGE);

10 DBMS_OUTPUT.PUT_LINE(MESSAGE);

11 WELCOME_PRINT(SITE, MESSAGE);

12 DBMS_OUTPUT.PUT_LINE(MESSAGE);

13 END;

14 /

SQL> EXECUTE WELCOME;

Welcome to MySpace.com

Welcome to rendc.org