TN3270 Error 520 When the Host Unbinds and Binds a Session

• Microsoft SNA Server, versions 2.0, 2.1, 2.11, and 2.11 Service Pack 1

SYMPTOMS

The TN3270 client loses its session, receiving an error 520. The Application Event Logs on the computer running SNA Server show an event 603 with the following description:

   TN3270E Service Error 520

   Internal LU session state error in FirstInboundByteProcess.
   State error id - 2 (expected CONT,SND,RCV).
   Current state - LU-LU, SNDNXMT

   >09/24 10:33:35.850 (+ smidgen )  Event=TEV_DataFromSNA
    Thread = 0x0000010B  Session = 0x00180478  Socket = 0x00000238
    VCB address=0x00180684
    verb_length=0x0044  verb=0x0052 (RUI)  opcode=0x8004 (WRITE)
    sid=0x000000A8  correlator=0x00180478  post_handle=0x00000150
    prim_rc=LUA_OK  sec_rc=LUA_SEC_RC_OK
    lu_norm    lua_data_length=0x00000000
    TH Only    efi=0  oadi=0  daf=00  oaf=00  snf=0002
    RH +RSP FMD fi=0   sdi=0  bci=1  eci=1  (Only)
    83 80 00    dr1=1  dr2=0  ri=0   qri=0  pi=0
                bbi=0  ebi=0  cdi=0  csi=0  edi=0  pdi=0

   >09/24 10:33:35.850 (+ smidgen )  Event=TEV_CRTOutboundWriteComplete
    Thread = 0x0000010B  Session = 0x00180478  Socket = 0x00000238
    State = OPER        InputState = IGNORE      OutputState = SNAREAD
    Toggle = LU-LU       LU State = SND         CanQueue = DATAPEND
    Bracket = INB         DTActive

   >09/24 10:33:35.860 (+ 10 msecs)  Event=TEV_LogicError
    FirstInboundByteProcess
    LUSessionStateConfused

CAUSE

A session status flag in the TN3270 Server is not being reset when the host unbinds and rebinds a session.

RESOLUTION

To resolve this problem, obtain the hotfix mentioned below.

STATUS

Microsoft has confirmed this to be a problem in SNA Server versions 2.0, 2.1, 2.11, and 2.11 Service Pack 1. This problem was corrected in the latest Microsoft SNA Server 2.11 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K