#include <db_cxx.h>
 
int
Db::set_feedback(void (*db_feedback_fcn)(DB *dbp, int opcode, 
                                         int percent));
      
         Some operations performed by the Berkeley DB library can take non-trivial amounts of time.
         The Db::set_feedback() method can be used by applications to
         monitor progress within these operations.  When an operation is likely to take a long time,
         Berkeley DB will call the specified callback function with progress information.
    
It is up to the callback function to display this information in an appropriate manner.
         The Db::set_feedback() method may be called at any time during the
         life of the application.
    
         The Db::set_feedback() method returns a non-zero error value on
         failure and 0 on success.
    
Berkeley DB is not re-entrant. Callback functions should not attempt to make library calls (for example, to release locks or close open handles). Re-entering Berkeley DB is not guaranteed to work correctly, and the results are undefined.
The db_feedback_fcn parameter is the application-specified feedback function called to report Berkeley DB operation progress. The callback function must take three parameters:
                                dbp
                            
The dbp parameter is a reference to the enclosing database.
                                opcode
                            
The opcode parameter is an operation code. The opcode parameter may take on any of the following values:
                                percent
                            
The percent parameter is the percent of the operation that has been completed, specified as an integer value between 0 and 100.