How to avoid parallel select-statements in the same sesssion

Vertica, at least as of now, is built so that you can only have one query running per session. Each connection handle can prepare, describe and execute exactly one statement handle. I also write client programs (in good old ANSI C in my case) - but, if I need several queries, nested or in parallel, to perform a task, each thread controlling a query acquires its own connection to Vertica. It always served my purpose ...

We solved the problem by using a mutex, like this:

             _mutex = new Mutex();
            _command.CommandText = "SELECT * FROM " + table;
            _mutex.WaitOne();
            VerticaDataReader reader = _command.ExecuteReader();
            reader.Close();
            _mutex.ReleaseMutex(); 

@joergschaber - Thanks for the update!