Oracle Tips by Burleson

Unconstrained Variables

Variables passed to procedures and functions  are unconstrained.  This allows greater reuse by not limiting the size of the passed variable.

create procedure full_name
  (publisher  in  varchar2,
   pub_cost  in  number,
   pub_date  in  date)

The publisher variable is defined as a varchar2 rather than a size-constrained varchar2(40).  This ensures that any varchar2 variable length can be passed to the publisher variable. 

The above book excerpt is from:

Easy Oracle PL/SQL Programming

Get Started Fast with Working PL/SQL Code Examples

ISBN 0-9759135-7-3   

John Garmany 

http://www.rampant-books.com/book_2005_1_easy_plsql.htm