LUA or EIS Application Must Enforce 3270 Bracket Protocol

ID: Q181736

The information in this article applies to:

Microsoft SNA Server, versions 2.11, 3.0, 4.0

SYMPTOMS

When using the SNA Server LUA API to communicate with a host application, the SNA Server expects the LUA application to detect and handle bracket errors on the session. This simplifies the detection and handling of bracketing errors and prevents potential problems if SNA Server simultaneously receives a Begin Bracket (BB) request from both the LUA application and the host.

If the LUA application has written a 3270 message to initiate a bracket (causing the session to be in a bracket state), and later receives a new bracket request from the host, the LUA application should send a negative response to the host bracket request and send sense code 08130001: Bracket Bid Reject: The component was in the in-bracket state when a bracket request was received.

CAUSE

The LUA application must enforce bracket protocols on the session.

RESOLUTION

The LUA application must be modified to reject bracket requests if already in an in-bracket state.

MORE INFORMATION

The following message flow describes a possible scenario where this problem may occur. In this case, the host application is not behaving properly with regard to bracketing protocols, and SNA Server expects the application to respond with a sense code (which it fails to do):


  LUA/RUI application   SNA Server service             Host
  ===================   ==================             =========
  RUI_WRITE (BC, BB, Data) ->
                        DLC FMD (RQE BC, BB, Data) ->
  RUI_WRITE (MC, Data) ->
         DLC FMD (MC) ->
  RUI_WRITE (MC, Data) ->
         DLC DATA (MC) ->
  RUI_WRITE (EC, CD, Data) ->
         DLC DATA (EC, CD) ->
                                                   <- DLC DATA (RQD BB, EB)
   <- RUI_READ complete (BB, EB, Data)
  RUI_WRITE (+RSP) ->
   <- RUI_WRITE -RSP (UNSUCCESSFUL / BRACKET ERROR)

Instead of issuing an RUI_WRITE (+RSP), the LUA/RUI application should have sent a negative response with sense data 08130001.

Additional query words:

Keywords : snalua snaprog sna3270 snaeis
Version : WINDOWS:2.11,3.0,4.0
Platform : WINDOWS
Issue type : kbprb