The major alternatives previously described are of interest to all VTAM® application program designers. Here are some additional facilities that not every user requires, but should be considered:

• The chaining of requests so that the number of responses required is minimized (CHAIN=ONLY or FIRST or MIDDLE or LAST)
• The quiescing of requests so that a sender may be told to temporarily stop sending when, for example, an input buffer is about to overflow (CONTROL=QEC)
• A method of communication that ensures that only the VTAM application program or the LU in session with it can be sending at one time, using either:
  • Quiesce protocol
  • Change-direction protocol.
• A method of communication that ensures that unexpected output from a VTAM application program is postponed until completion of an existing transaction (bracket protocol).