To create a transient table, use the following command:
CREATE TRANSIENT TABLE <...>;
where <...> denotes syntax that is the same as for any other type of table.
Transient tables are always in-memory tables. If you use the STORE DISK clause, the server will give you an error. If you use STORE MEMORY, or if you omit the STORE clause altogether, the server will create the transient table as an in-memory table.