Supporting IBM CICS LU 6.2 Transactions

Applies To: Windows Server 2008

The Microsoft Distributed Transaction Coordinator (MS DTC) can participate in distributed transactions with IBM systems that support the LU 6.2 protocol. If the connection between the Windows-based system and the IBM-based system fails and remains shut down, a transaction outcome can remain in doubt for an extended period of time. In this event, the IBM system may heuristically commit or abort the transaction. Essentially, this means that the IBM-based system guesses the transaction's outcome rather than waiting to be told its outcome. Having heuristically committed or aborted the transaction, the IBM system can then release the locks that are held on behalf of the transaction. This allows other applications to access the records that the transaction updated and locked.

When you restore the connection between the Windows-based system and the IBM-based system, the DTC transaction manager compares the actual transaction outcome with the IBM system's heuristic decision about the transaction. The DTC reports the event in the application event log if the IBM-based system aborted the transaction or reported a heuristic mixed outcome when the DTC committed the transaction.

The DTC also reports the event in the application event log if the IBM-based system mistakenly aborted the transaction or reported a heuristic mixed outcome or if the IBM-based system aborted the transaction or reported a heuristic mixed outcome when the DTC aborted the transaction.