You can set the "TraceOn" param in the "[Parameters]" section of the Virtuoso configuration file such that it is enabled on server startup as detailed at: http://docs.openlinksw.com/virtuoso/databaseadmsrv.html#ex_traceoniniopt [Parameters] .... TraceOn = soap, errors ... This will enable logging of additional information regarding SOAP calls and SQL run-time errors into the virtuoso.log file.