APPC Allocation Error Running Multithreaded Random & Bounce TP (140833)

SYMPTOMS

When you run 4 to 5 copies of the Random & Bounce transaction program (TP) with 8 threads each, the APPC Allocate() verb fails with error:

 - Primary Return Code: 0003: AP_ALLOCATION_ERROR
 - Secondary Return Code: 084C0000: AP_TRANS_PGM_NOT_AVAIL_NO_RETRY

The APPC return codes are logged after about 500,000 APPC verbs are executed.

This problem was found using test applications and only under very heavy stress, when invoking a TP over 65000 times, therefore, this symptom rarely occurs.

CAUSE

When the invoked TP issues the Receive_Allocate() verb and the Receive_Allocate() verb decrements the semaphore counter, the decrement of the semaphore counter (WaitForSingleObject())is done only when there are no pending Allocate()s waiting, instead of every time a Receive_Allocate() is processed.

Each time a dload (Incoming Allocate ()) is processed by SnaBase a semaphore counter is increased (ReleaseSemaphore()) by one. After the semaphore counter has reached 65535, the ReleaseSemaphore() call fails with the following error:

Error 289: ERROR_TOO_MANY_POSTS

The SnaBase that processes the incoming Allocate() does not log any errors. However, the SnaServer who sent the Allocate() request, logs the following error in the Event Viewer:

Event ID: 60

Failed to invoke APPC TP <value> (value), sense data = 084C0000

EXPLANATION: An attempt to invoke the APPC TP shown has failed.

The most common cause of this error (084c0000) is due to configuration problems where the invokable TP is not registered properly on an SNA Server in the domain.

RESOLUTION

The semaphore counter is now decremented every time a Receive_Allocate() is processed.

Also, the SnaBase that processes the incoming Allocate(), logs a new error:

Error 703 subcode 1015 - ReleaseSemaphore() failed.

There following six subcodes describe other possible allocate errors:

   1010 - The server who sent the dload message was not found in the local
          service table.
   1011 - The TP to be invoked was not found in the service table.
   1012 - DMOD failed to create a new service table entry for the
          Non-Queued TP.
   1013 - DMOD failed to create a new service table entry for the Queued
          TP.
   1014 - OpenSemaphore() failed.
   1016 - DMOD failed to start the TP (NT service or application).

Microsoft has an update for the following Windows 95 client files only:

<Win95_root>\SYSTEM\DMODAPPC.DLL
<Win95_root>\SYSTEM\SNADMOD.DLL

STATUS

Microsoft has confirmed this to be a problem in SNA Server for Windows NT. This problem was corrected in the latest SNA Server for Windows NT, 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