Changing a table from in-memory to disk-based or vice-versa
If the table is empty, you can alter the type of a table from in-memory table to disk-based table or vice versa. To do this, use the following command:
ALTER TABLE table_name SET STORE MEMORY | DISK
If the table contains data, you need to create a new table with different name to which you copy the data. After copying the data to the new table, you can drop the old table and rename the new table with the same name as the original table.