When writing your exit routine, remember that any number of vectors can exist and that vector lengths might be different in different releases of VTAM®. Therefore, use the length byte in the environment vectors list to identify the end of the parameter list. In addition, use a vector's length field to manipulate the length of any vector in the parameter list. If you use these length fields, it is less likely that you will have to recode your existing exit routine if bytes are added to a vector, or vectors are added to the parameter list.