Command and RU types in VTAM messages

This chapter lists the command and request/response unit (RU) types that can appear in VTAM® messages. See z/OS Communications Server: SNA Operation for additional information on commands. See SNA Formats for additional information on RUs.

There are two RU types that represent internal VTAM RU flows. These internal RU types are not documented in SNA publications and some are not included in VTAM Data Areas .

It is not required that users of the product know the meaning of these internal RUs. When required, the product support organization might use them to assist in internal flow diagnosis.
  • Access Method RU (AM type)
    • These internal RUs are requests that might be seen in the PIU trace and are a function of physical unit services (PUNS), configuration services, or session services.
  • Interprocess Signals (IPS type)
    • These internal signals are issued for APPN functions. They can be seen in APSEND trace entries.