Raise the SNR

Here’s the rundown on my most recent admin nightmare. I was helping to get Microsoft Distributed Transaction Coordinator working between 2 Windows XP SP2 boxes. These are development machines on which we wanted to prototype distributed transactions. In our case, we wanted to update 2 different SQL Server databases on 2 separate machines, and allow the updates to be committed on both systems in the case of success, or rolled back if an error occurred on either system. This is known as Two Phase Commit.

SECURITY WARNING!
The following changes could expose your system to security risks. This was implemented on development systems to test prototype code. If you need to make this work on a production system, please consult a qualified Microsoft Server Professional to implement MSDTC in your environment.

To make DTC work, a few changes have to be made to XP SP2. Here’s the list:

Open the following firewall ports

• TCP Port 1433 (Default port used by SQL Server)
• UDP Port 1434 (Used by SQL Server)
• TCP Port 3372 (Used by MSDTC.EXE)
• Add MSDTC.EXE to the firewall as an allowed program

Add the following entries to the registry if they don’t already exist in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Rpc\ClientProtocols – Found in MS Knowledge Base Article 325930

• ncacn_http REG_SZ rpcrt4.dll
• ncacn_ip_tcp REG_SZ rpcrt4.dll
• ncacn_np REG_SZ rpcrt4.dll
• ncadg_ip_udp REG_SZ rpcrt4.dll

Run dcomcnfg.exe to modify the security for MSDTC

• Navigate to “Component Services\Computers\My Computer” in the tree view in the left-hand pane.
• Right-click on My Computer and select properties
• On the MSDTC tab, click on the “Security Configuration…” button
• Change the security settings to match the following:

MSDTC Security Config Dialog

SECURITY WARNING!
The preceding changes could expose your system to security risks. This was implemented on development systems to test prototype code. If you need to make this work on a production system, please consult a qualified Microsoft Server Professional to implement MSDTC in your environment.