SyncPoint Support Synchronization (Exchange Log Names) Failure After CICS Cold Start (237867)

SUMMARY

This article describes a customer's problem incurred in a production application after the computer running COM Transaction Integrator for CICS and IMS (COMTI) was upgraded to Windows NT 4.0 Server Service Pack 4 from Windows NT 4.0 Server Service Pack 3.

The customer's COMTI application runs in a two phase commit environment, which uses IBM Sync Level 2 protocol to extend a two phase commit to the mainframe CICS environment. The CICS region on the mainframe, according to the customer's standard operating procedure, is stopped each morning and restarted with a COLD start initialization. After the COLD start initialization and before Windows NT 4.0 SP4 was installed, the application could then be used successfully.

However, after installing Windows NT 4.0 SP4, the following entry would appear in the Event Log after the CICS region was cold started and the COMTI application would return a user-defined error message to the client.

   Event ID: 120
   Source: COMTI Resync TP
   Type: Error
   Category: General

   (120) The Resynchronization Service failed on a
      Log Name Exchange (XLN) initiated by the LOCAL LU.
  
  EXPLANATION
   Local LU llllllll and host LU hhhhhhhh failed to synchronize
    logs. Local log state was WARM. Host log state was COLD.
   DTC XLN Confirmation Code was 2

The prior event log entry may be followed by:

   Event ID: 116
   Source: COMTI Resync TP
   Type: Error
   Category: General

   (116) The Resynchronization Service failed to handle an
   exchange log name request from a Remote Environment.
  
   EXPLANATION
    The Resynchronization Service encountered HRESULT 8004ee0d
    while trying to exchange log names (XLN) between
    local LU llllllll and host LU hhhhhhhh.

The customer discovered that rebooting the COMTI computer cleared up the problem.

A permanent solution was discovered when the Microsoft Distributed Transaction Coordinator (DTC) log was reset. After that, the problem no longer occurred with successive CICS cold starts.

MORE INFORMATION

In a two phase commit situation, such as this, there must have been a successful Exchange Log Names (XLN) between Microsoft Distributed Transaction Coordinator on the COMTI computer and the CICS region on the mainframe before a new COMTI transaction can be enlisted on DTC. The XLN needs to occur after an outage of either partner in the two phase commit operation. It serves to get all partners synchronized as to the state of any pending transactions. In this case, the CICS region was stopped and started in the morning and an XLN is therefore necessary. It failed due to some unexplained problem involving the DTC log.

To reset the DTC log, launch DAC.exe and select the "Advanced" tab. In the "Log" section of the dialog box, click Reset Log.

Besides the prior example, Microsoft recommends that a CICS region be initialized with a WARM start when involved with COMTI applications that uses a two phase commit and IBM Sync Level 2. This will cause CICS to retain a "memory" of pending transactions that can be resolved during a CICS WARM start initialization at the time of the XLN.