The GETBUF macro can be used with the basic access method to request a buffer from a buffer pool constructed by the BUILD, GETPOOL, or OPEN macro. That buffer pool resides below the 16 MB line even if you issue BUILD, GETPOOL, or OPEN in 31-bit mode. The address of the buffer is returned by the system in a register you specify when you issue the macro. If no buffer is available, the register contains a 0 instead of an address.