IBM DOS/VS COBOL permits an optional PROCESSING MODE clause in a SELECT statement (also called a file-control-entry):
PROCESSING MODE IS SEQUENTIAL
IBM DOS/VS COBOL ignores this clause. Compatibility with IBM DOS/VS COBOL requires that ACUBOL-GT ignore it also.
You may put a PROCESSING MODE clause into a SELECT statement, but only when the compiler is in the IBM DOS/VS COBOL compatibility mode.
Put the PROCESSING MODE clause in any convenient spot after the ASSIGN clause.