Because HPDT is targeted for use by large packet applications that are moving large amounts of data, VTAM's processing of HPDT send requests differ from the processing of normal APPCCMD send requests. The following describes these differences.

• All HPDT send requests require that the data is flushed. If an APPCCMD CONTROL=SEND, QUALIFY=DATA macroinstruction is issued with OPTCD=XBUFLST specified, the data is flushed.
• Logical record length checking for HPDT send requests is bypassed. For normal send processing, VTAM® performs logical record checking. Because the users of HPDT are authorized, they are expected to be correctly written and to have provided the data correctly. Bypassing logical record length checking saves pathlength for HPDT applications.
  Note: Logical record checking is turned off for the duration of a conversation for all sends, including non-HPDT sends, once the first HPDT send is issued.