The use of the BUFFLST option for LU 6.2 functions is somewhat different than for non-APPCCMD SEND macroinstructions. Application programs cannot supply a request header (RH) to be associated with the data. VTAM® creates the RH using information in the RPL fields. In addition, application programs cannot use the LMPEO function in VTAM to control the splitting or segmenting of data within or across SNA request units. VTAM determines where RU boundaries fall within the data and when a current RU ends and a new RU begins. Application programs can, however, control data within RUs in an indirect way by using the APPCCMD CONTROL=SEND, QUALIFY=FLUSH macroinstruction to force VTAM to send data out. This is, however, independent of whether the application program uses the BUFFLST function.