#include <db.h> int DB_ENV->mutex_free(DB_ENV *dbenv, db_mutex_t mutex);
            The DB_ENV->mutex_free() method discards a mutex allocated by 
            DB_ENV->mutex_alloc().
    
             The DB_ENV->mutex_free() method may not be called before the 
             DB_ENV->open()  method is called.
    
         The DB_ENV->mutex_free() 
            
                  method returns a non-zero error value on failure and 0 on success.
            
            
        
    
The mutex parameter is a mutex previously allocated by DB_ENV->mutex_alloc().
                         The DB_ENV->mutex_free() 
            
                 method may fail and return one of the following non-zero errors: