What are the system resources of your database server? Is their sufficient disk space?
The logging available to Direct Discovery is by way of ODBC logging.
Direct Discovery SQL statements passed to the data source can be recorded in the trace files of the database connection. For a standard ODBC connection, tracing is started with the ODBC Data Source Administrator:
My server memory is 256GB , My file log is as following:
(2014-05-31 12:40:04) Information: The Source Document reload complete. DocumentPath=F:\BI\DEPLOY\STOCK.qvw
(2014-05-31 12:40:04) Information: Memory Allocation Delta for this file=435.48 Mb. Available Physical Memory Before Reload=371818.34 Mb. Available Physical Memory After Reload=373737.98 Mb. Total Physical Memory=373737.98 Mb.
(2014-05-31 12:40:04) Error: The Source Document was NOT reloaded successfully. DocumentPath=F:\BI\DEPLOY\STOCK.qvw.
(2014-05-31 12:40:04) Information: Closing the document.