IMS Programs May Lock after COMTI Posts a Backout Operation (193828)

SUMMARY

In testing COMTI components that require transactions interoperating with IMS version 6.0, Microsoft has observed unexpected behavior when the transaction does not come to a successful conclusion on all systems. When MSDTC determines that the transaction cannot be committed, it causes COMTI to send a back-out indication to IMS. In order to back out the application, IMS issues an ABEND, code 0711, in the MPR (Message Processing Region). This returns the application's data to its original state, but causes undesirable consequences. The IMS transaction and program are left in a stopped state and must be manually started by the master terminal operator before COMTI can resume operations with them. The SNA conversation is abnormally terminated, which causes a number of events to be posted to the Windows NT application event log, indicating problems with the COMTI SNA transport.

MORE INFORMATION

(203) The COM Transaction Integrator state machine's call to the transport's Abort method failed.

HRESULT: 0x80020009

Explanation: The COM Transaction Integrator state machine's call to the Abort method on the transport object failed unexpectedly. This is probably caused by a problem with the LU6.2 transport. Normal transaction aborts do not generate this event.

Action: Look for related event log entries from the COM Transaction Integrator transport object or SNA Server to may provide additional information.

Also, MSDTC does not know the disposition of the transaction after the conversation ABENDs, so it initiates a recovery sequence to make sure it is backed out, leaving this event in the log:

(122) The Resynchronization Service performed successful transaction recovery.

Explanation: Local LU xxxxxxxx and host LU yyyyyyyy agreed on the final state of the transaction. Local transaction state was RESET. Host transaction state was 1, where:

1 = RESET
3 = IN_DOUBT
4 = COMMITTED
5 = HEURISTIC_RESET
6 = HEURISTIC_COMMITTED
7 = HEURISTIC_MIXED

Logical Unit of Work ID = SGPHL1.L1163000 07CE091E0E150001

Action: No Action is necessary.

If the host reported a heuristic decision for the transaction due to host configuration or operator action, the outcome selected for the transaction was correct.

If the client program subsequently attempts a new method before the IMS transaction has been started again, it will receive the following exception, which is also recorded in the event log:

(102) COM Transaction Integrator reported the following exception to the client:

Component: IMS2PH.TRANSACTIONS.1
Method: TRANUPDT

Exception description:
(1429) Transaction TRANUPDT at host LU IMSMLU62 could not load the server program.

See the Windows NT Event Log on the COMTI computer for SNA error log data, including possible host ABEND code. Review the host region configuration.

Explanation: An Automation exception representing an error condition was returned to a COM Transaction Integrator client. The description shown above contains more information about the exception that was reported.

Action: The exception may be caused by communication problems or errors in your Host application. See the exception description for corrective actions.

IBM has stated that this behavior by IMS is as intended. However, Microsoft does not believe that this is a correct implementation of the protocols specified in IBM's Systems Network Architecture: Sync Point Services Reference (SC31-8134-00, p2-67). This reference states that the system that receives the Backout (FMH-7) should reply positively and leave the conversation intact. We are continuing to work with IBM to seek a resolution on this issue.

NOTE: The data integrity is not jeopardized by the inconvenient behavior described above. The back-out operations are successfully issued in each environment.