Most of the error feedback for APPCCMD macroinstructions is found in the RPL extension fields RCPRI and RCSEC. The principal cause of the error is described in RCPRI, with RCSEC further qualifying the description.
Many of the RCPRI,RCSEC combinations indicate whether the error is the result of a temporary condition or a more serious problem. Some combinations indicate whether the macroinstruction should be issued again. (To determine these combinations, refer to z/OS Communications Server: SNA Programmer's LU 6.2 Reference.) The return codes also indicate if data was lost when sending or receiving data.
Error return codes can report changes in the state of the conversation. For example, an error return code on an APPCCMD CONTROL=SEND macroinstruction can mean that side of the conversation has been placed in RECEIVE state. The application program can determine the conversation state by examining the RPL6CCST field at the completion of most APPCCMD macroinstructions. If the application program is maintaining conversation states, it should update the conversation state in such cases.
Each possible variation of the APPCCMD macroinstruction is listed in the z/OS Communications Server: SNA Programmer's LU 6.2 Reference with a complete list of possible return codes for that macroinstruction. You should use that list as a starting point for deciding which return codes your application program should process.
Error return codes might not be caused by the macroinstruction on which they are returned. Allocation errors, for example, are frequently reported on APPCCMD macroinstructions issued after APPCCMD CONTROL=ALLOC. An application program could issue APPCCMD CONTROL=ALLOC and several APPCCMD CONTROL=SEND macroinstructions before any data is actually sent through the network. When designing your application program, you should keep in mind that errors reported by the partner LU might not necessarily pertain to the macroinstruction with the nonzero return code. Errors such as parameter errors or state errors are detected by VTAM® when the macroinstruction is issued and will pertain to the macroinstruction with the nonzero return code.