#include <db.h> int DB_ENV->mutex_unlock(DB_ENV *dbenv, db_mutex_t mutex);
            The DB_ENV->mutex_unlock() method unlocks the mutex locked by 
            DB_ENV->mutex_lock().
    
         The DB_ENV->mutex_unlock() 
            
                  method returns a non-zero error value on failure and 0 on success.
            
            
        
    
The mutex parameter is a mutex previously locked by DB_ENV->mutex_lock().
                         The DB_ENV->mutex_unlock() 
            
                 method may fail and return one of the following non-zero errors: