SELECT clause

The SELECT clause identifies a file in the COBOL program to be associated with an external data set.

SELECT OPTIONAL
Can be specified only for files opened in the input, I-O, or extend mode. You must specify SELECT OPTIONAL for those input files that are not necessarily available each time the object program is executed. For more information, see OPEN statement notes.
file-name-1
Must be identified by an FD or SD entry in the DATA DIVISION. A file-name must conform to the rules for a COBOL user-defined name, must contain at least one alphabetic character, and must be unique within this program.

When file-name-1 specifies a sort or a merge file, only the ASSIGN clause can follow the SELECT clause.

If the file connector referenced by file-name-1 is an external file connector, all file-control entries in the run unit that reference this file connector must have the same specification for the OPTIONAL phrase.