#include <db_cxx.h> void DbEnv::set_error_stream(class ostream*);
When an error occurs in the Berkeley DB library, an exception is thrown or an errno value is returned by the interface. In some cases, however, the errno value may be insufficient to completely describe the cause of the error, especially during initial application debugging.
         The DbEnv::set_error_stream() and
         Db::set_error_stream()
         methods are used to enhance the mechanism for reporting error messages to the
         application by setting the C++ ostream used for displaying
         additional Berkeley DB error messages.  In some cases, when an
         error occurs, Berkeley DB will output an additional error message
         to the specified stream.
    
The error message will consist of the prefix string and a colon (":") (if a prefix string was previously specified using Db::set_errpfx(), an error string, and a trailing <newline> character.
Setting stream to NULL unconfigures the interface.
            Alternatively, you can use the 
            DbEnv::set_errfile() or 
            Db::set_errfile() methods 
            to display the additional information via a C Library FILE *, 
            or the DbEnv::set_errcall() 
            and Db::set_errcall()
            methods to capture the additional error information in a way that does not use either 
            output streams or C Library FILE *'s. 
            You should not mix these approaches.
    
This error-logging enhancement does not slow performance or significantly increase application size, and may be run during normal operation as well as during application debugging.
         The DbEnv::set_error_stream() method configures operations
         performed using the specified DbEnv handle, 
         not all operations performed on the underlying database environment.
    
         The DbEnv::set_error_stream() method may be called at any time during the
         life of the application.