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

If REVERSED is specified, then:
◦ Neither LOCK nor PROMPT prompt-item can be specified.
◦ REVERSED cancels the effect of GENERIC (a positioning mode that the START statement
can specify).
REVERSED is not recommended if these conditions are true, because it is very inefficient:
◦ File organization is RELATIVE.
◦ The relative key is the key of reference.
◦ Records are not contiguous.
• Action of the READ Statement (Sequential Read)
Any READ statement that has a NEXT or REVERSED phrase, or is associated with a file for
which the ACCESS MODE SEQUENTIAL clause is specified or implied, is a sequential READ
statement. Any other READ statement is a random READ statement.
The file identified by file-name must be open in the INPUT or I-O mode; if it is not, the
read operation is unsuccessful with I-O status code “47.” If the file is described with fixed-length
records and a smaller record is read, the read operation is successful with I-O status code
“04.”
In addition to the specific I-O status codes described later, the general codes “00,” “30,” and
“90” can occur. For more information, see I-O Status Code (page 247).
◦ Retrieval of a logical record
The read operation retrieves a logical record from the file identified by file-name and
places it into the record area associated with that file.
◦ Alignment within record area
If the size of the retrieved record is greater than the maximum record size defined for the
file (as specified in the explicit or implicit RECORD clause in the file description entry for
file name), the run-time routines truncate the retrieved record on the right before placing
it in the record area.
If the size of the retrieved record is less than the maximum record size defined for the
file, the run-time routines left justify the record content within the record area. All character
positions in the record area that are to the right of the last character in the retrieved record
have undefined values—that is, they can contain any characters. If you want to verify
that they are spaces, use the INTO phrase.
When the read operation is attempted on a file with fixed-length records and the size of
the retrieved record is greater than the maximum record size defined for the file or less
than the minimum record size defined for the file (as specified in the explicit or implicit
RECORD clause in the file description entry for the file), the read operation is unsuccessful
with I-O status code “30” and the GUARDIAN-ERR register has the value 21.
◦ Unsuccessful read operation
Whenever the read operation terminates with an I-O status code greater than or equal
to “30” (except “97”), execution of the READ statement is not successful. In this case the
applicable USE procedure, if one exists, is executed.
If the execution of a READ statement is unsuccessful for any reason, the key of reference
and the contents of the record area associated with the file are undefined and the value
of the depending item, if one is defined for the file, is not altered.
408 Procedure Division Verbs