Fix XACT_E_WRONGUOW 0x8004D012 – MSDTC Unit of Work Error

Quick answer: Restart the MSDTC service and clear its log. This error means a transaction's unit of work ID doesn't match what the resource manager expects.

Quick Answer

Restart the MSDTC service and clear the DTC log. If that doesn’t work, check for stale transaction contexts in your application code or rebind the COM+ component.

What’s Happening Here

This error pops up when a resource manager – typically SQL Server or a COM+ application – gets handed a transaction unit of work (UOW) that doesn’t match its own records. Think of it like a key that doesn’t fit the lock. The transaction was either already committed, rolled back, or never existed on that resource manager. I see this most often in three scenarios: after a DTC service crash, when a web app reuses a stale transaction object, or when two different DTC instances get crossed in a load-balanced setup.

Fix Steps

Restart the MSDTC service. Run net stop msdtc && net start msdtc as Administrator. This clears in-memory transaction state without touching the log file. Nine times out of ten, this alone fixes it temporarily.
Clear the DTC log file. If the error comes back after a restart, the log is corrupt. Stop MSDTC, delete the log, then restart. The log lives at C:\Windows\System32\Msdtc\MSDTC.LOG. Run:
```
net stop msdtc
cd %SystemRoot%\System32\Msdtc
del MSDTC.LOG
net start msdtc
```
Windows recreates the log on restart. Only do this if you’re OK losing any pending distributed transactions (which you likely don’t have if you’re hitting this error).
Check DTC security settings. Open Component Services (dcomcnfg), go to Distributed Transaction Coordinator > Local DTC > Properties > Security. Enable Network DTC Access, Allow Remote Clients, Allow Inbound, and Allow Outbound. Apply and restart DTC. This fixes communication mismatches in cross-server transactions.
Rebind COM+ components. If you’re using COM+ transactions, the component might have a stale reference. Use regsvr32 on the component DLL or reinstall the COM+ application. Run regsvr32 /u YourComponent.dll then regsvr32 YourComponent.dll.

If That Doesn’t Work

Try these in order:

Check for orphaned transactions in SQL Server. Run SELECT * FROM sys.dm_tran_active_transactions and look for open transactions with a NULL or stale UOW. Kill them with KILL <session_id>.
Review your application code. Don't cache TransactionScope objects. Create a new one per operation. In .NET, wrap it in a using block and let it dispose naturally.
Update DTC to use a specific CID. Rare, but if you have multiple DTC instances, set the CID via registry: HKLM\Software\Microsoft\MSDTC\CID. Set it to a unique GUID. Reboot.

Prevention Tips

Always use using blocks or explicit Dispose() calls for transaction objects. Leaked transactions = stale UOWs.
Monitor DTC log size. A log over 10 MB often signals corruption. Set a scheduled task to restart DTC weekly if you see it grow.
In load-balanced web farms, use a single DTC instance or configure consistent routing. Crossed DTCs cause this error every time.

One last thing: don’t bother reinstalling Windows or the DTC role for this error. That’s like using a sledgehammer on a pushpin. The log clear and service restart handles 95% of cases.