When a sending and a receiving item in a statement share a part of their storage areas,
yet are not defined by the same data description entry,
the result of the execution of such a statement is undefined.
Overlapping moves are detected at compile time only when the MOVE verb is used and neither operand uses reference modification or subscripting. Forward overlapping moves result in a warning message, if you set the Compiler directive WARNING"3". Any other types result in flagging messages, if you set the Compiler directive FLAG"dialect", where "dialect" is anything but OSVS. Other operations resulting in sending and receiving items sharing the same memory are not detected.
Although portability of COBOL source code is only guaranteed when there are no overlapping MOVE statements, this COBOL system does allow such statements. The behavior of such statements is sensitive to the BYTE-MODE-MOVE Compiler directive.