To force alignment
Use the DS instruction to align the instruction or data that follows,
on a specific boundary. You can align the location counter to a doubleword,
a fullword, or a halfword boundary by using the correct constant type
(for example, D, F, or H) and a duplication factor of zero. No space
is reserved for such an instruction, yet the data that follows is
aligned on the correct boundary. For example, the following statements
set the location counter to the next doubleword boundary and reserve
storage space for a 128 byte field (whose first byte is on a doubleword
boundary).
DS 0D
AREA DS CL128
Alignment is forced whether or not the ALIGN assembler option is set.