Microsoft KB Archive/172801

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TN3270 Client Session Lost Using PF Keys to Toggle Screens

Article ID: 172801

Article Last Modified on 7/13/2004


  • Microsoft SNA Server 3.0
  • Microsoft SNA Server 2.11 Service Pack 1
  • Microsoft SNA Server 2.11 Service Pack 2
  • Microsoft SNA Server 3.0 Service Pack 4
  • Microsoft SNA Server 4.0

This article was previously published under Q172801


When you rapidly press the PF2 and PF12 keys to toggle between host screens from a TN3270 client, the client's session is lost and the following error message is displayed:

TN3270E Service Error 505
SNA API verb READ failed. Failure described as:

RUI read verb has completed with primary rc of Negative Response and
secondary rc of OK

Within an SNA Server TN3270 internal trace, the RUI_READ request is failing with primary_rc = 0018 (LUA_NEGATIVE_RESPONSE), followed by the TN3270 server calling RUI_TERM to terminate the session.


Quick toggling of the PF keys causes a race condition, which results in TN3270 Service receiving LUA_NEGATIVE_RESPONSE error from an RUI function call. The TN3270 server treats this error as a fatal condition, causing the TN3270 Server to close the session.


Microsoft has confirmed this to be a problem in SNA Server versions 2.11, 2.11 Service Pack 1 (SP1), and 2.11 SP2. A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

Microsoft has confirmed this to be a problem in SNA Server versions 3.0 and 3.0 Service Pack 1 (SP1). This problem was corrected in the latest SNA Server version 3.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):



With the fix applied, the TN3270 Server treats this error as a non-fatal condition and keeps the session active.

Keywords: kbbug kbfix kbnetwork KB172801