An external subroutine can access the global data area used

by the invoking object(Program, Subprogram)

Moreover, parameters can be passed with the PERFORM

statement from the invoking object to the external

subroutine. These parameters must be defined either in the

DEFINE DATA PARAMETER statement of the subroutine, or in a

parameter data area used by the subroutine. Programs,

Subprograms and Subroutines Programming Guide

In addition, an external subroutine can have its local data

area, in which the fields that are to be used only within

the subroutine are defined.

However, an external subroutine cannot have its own global

data area.