COBOL Manual for TNS/E Programs (H06.08+, J06.03+)

The MESSAGE SOURCE clause provides a mechanism through which a COBOL program can
discover the sender of each message received. During the successful execution of a read operation
on $RECEIVE, the $RECEIVE mechanism places a set of values into the storage space designated
in the MESSAGE SOURCE clause.
Example 261 MESSAGE SOURCE Format
01 SOURCE-MESSAGE.
05 SYSTEM-FLAG PICTURE S9
USAGE IS COMPUTATIONAL.
05 ENTRY-NUMBER PICTURE 999
USAGE IS COMPUTATIONAL.
05 FILLER PICTURE X(4).
05 PHANDLE PICTURE X(20).
05 FILLER PICTURE X(4).
If the value of SYSTEM-FLAG is -1, the message came from the operating system.
For more information about the MESSAGE SOURCE phrase, see MESSAGE SOURCE Phrase
(page 149). For more information about the Receive-Control paragraph, see Chapter 31: Process
Initiation, Communication, and Management (page 915).
Intercepting Operating System Messages 837