JR44762: CSWIN - TRAP IN TN3270 SERVER

Communications Server for Windows, Version 6.4 -- Latest Fixpack

APAR status

• Closed as program error.

Error description

• Communications Server for Windows
  ---------------------------------
  TN3270 clients lose connection to the server. On the server, Dr.
  Watson logs a trap:
  
  Application exception occurred:
  App: TN3270WN.EXE (pid=4868)
  Exception number: c0000005 (access violation)
  

Local fix

• Restart the server.
  

Problem summary

• The trap data shows two problems:
  1) If a client sends in multiple connection requests too
  quickly, a memory initialization bug can be hit, because a
  certain control block was not being initialized properly. This
  could lead to an attempt to re-use an expired semaphore, causing
  the trap.
  
  2) This was exposed by fixing problem (1). If a client requestes
  an LU that is not defined on the host, the server may return the
  error response without waiting for internal processing to
  complete. If the request is repeated too quickly, it could
  overwrite the first request and cause the server to hang.
  

Problem conclusion

• Code has been corrected to properly initialize the control block
  at each new client connection. Code has also been corrected to
  prevent conflict with multiple requests for a non-existant LU.
  

Temporary fix

• TN3270WN.EXE
  TN3270D.DLL
  

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  JR41157

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  COMM SERV NT 6.

• Fixed component ID

  5639F2503

Applicable component levels

• R640 PSY