The EXTERNAL clause specifies that the storage associated with a data item
is associated with the run unit rather than with any particular program within
the run unit.

EXTERNAL Clause - Format
>>-+----+--EXTERNAL--------------------------------------------><
'-IS-'
An external data item can be referenced by any program in the run unit
that describes the data item. References to an external data item from different
programs using separate descriptions of the data item are always to the same
data item. In a run unit, there is only one representation of an external
data item.
The EXTERNAL clause can be specified in either 01 level entries in the
Working-Storage Section or in file description entries. If there are two data
description entries with the same data name in the same Data Division, only
one entry can contain the EXTERNAL clause. Index-names, condition-names, and
renaming (level-66) items in an external data record do not possess the EXTERNAL
attribute.
The data contained in the record named by the data-name clause is external
and can be accessed and processed by any program in the run unit that describes
and, optionally, redefines it. This data is subject to the following rules:
- If two or more programs within a run unit describe the same external data
record, each record-name of the associated record description entries must
be the same and the records must define the same number of standard data format
characters. However, a program that describes an external record can contain
a data description entry including the REDEFINES clause that redefines the
complete external record, and this complete redefinition need not occur identically
in other programs in the run unit.
- Use of the EXTERNAL clause does not imply that the associated data-name
is a global name.
- The VALUE clause must not be used in any data description entry which
includes, or is subordinate to an entry which includes, the EXTERNAL clause.
The VALUE clause can be specified for condition-name entries associated with
such data description entries.
- The TYPEDEF clause cannot be specified in the same data description entry
as the EXTERNAL clause.
See Data Reference and Name Scoping for more information.