In-Memory Database Guide : Working with in-memory tables
  
Working with in-memory tables
When creating tables, you specify the table type you want to use as part of the CREATE TABLE statement. By default, new tables are created as persistent in-memory tables. You can also change the table type of tables that have no data.
See also
How to decide which tables to designate as in‑memory tables
Creating in-memory and disk-based tables
Creating temporary and transient tables
Changing a table from in-memory to disk-based or vice-versa