When you run Dcpromo to promote or demote a domain controller, it builds a Dcpromoui.log and Dcpromo.log file.
You can use these log files to troubleshoot problems with the promotion or demotion of your domain controllers.
You can control the level of detail that the Dcpromoui.log log records by setting a bit mask into the DCPROMOUI Value Name, a REG_DWORD data type, at HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\AdminDebug.
The first (left-most) 16 bits of the REG_DWORD is the logging level mask:
0x0002 Trace constructor and destructor calls. 0x0004 Trace AddRef and Release calls. 0x0008 Trace function entry and exit. 0x0010 Output trace messages. 0x0020 Output log header with build and time stamp. 0x0040 capture the call stack for each invocation of operator new (chk build only).The second (right-most) 16 bits control the output options:
0x0001 Output to file in the %SystemRoot%\Debug folder. 0x0002 Output to debugger (OutputDebugString).To set the maximum logging level detail and output to the %SystemRoot%\Debug\Dcpromoui.log file, set the DCPROMUI data value to FF0003, using the Hex radix.
NOTE: If you search the Dcpromoui.log file for logging mask, you will find the DCPROMOUI data value used to create the log. If the DCPROMOUI data value is FF0003, it will be displayed in the Dcpromoui.log file as 00FF.