Declares an approximate number of threads in the database environment.
                The syntax of the entry in in the DB_CONFIG file is a
                single line with the string
                set_thread_count, one or more whitespace
                characters, and the thread count.  The DB_CONFIG file is
                read when the database environment is opened, and hence it
                silently overrules configuration done before that time.
            
For more information, see DB_ENV->set_thread_count().