Use the ALTER TABLE ... SET STORE DISK or SET STORE MEMORY statement to change whether the table is stored in memory or on disk.
A table can be changed from disk-based to in-memory or in-memory to disk-based only if the table is empty. If you try to change a table to the same storage mode that it already uses (for example, if you try to change an in-memory table to use in-memory storage), then the statement has no effect, and no error message is generated.