An Oracle Database 23ai instance has INMEMORY_SIZE set to 10 GB and INMEMORY_AUTOMATIC_LEVEL set to HIGH. Several application tables are created without specifying any INMEMORY clause. How does the database manage these tables regarding the In- Memory Column Store (IMCS)?

When INMEMORYAUTOMATICLEVEL is set to HIGH, Automatic In-Memory (AIM) is fully enabled. AIM uses the database's heat map and other usage statistics to identify segments that would benefit most from being in the In-Memory Column Store (IMCS). For "hot" segments created without an INMEMORY clause, AIM will automatically issue an ALTER TABLE ... INMEMORY command to enable them for the IMCS and then trigger their population. This automates the management of the IMCS, ensuring optimal performance without manual DBA intervention.

B. This describes the behavior when INMEMORYAUTOMATICLEVEL is OFF or LOW, where AIM does not automatically add objects to the IMCS.
C. Using a tablespace's INMEMORY attribute is one method of population, but INMEMORYAUTOMATICLEVEL=HIGH enables object-level automation regardless of the tablespace setting.
D. AIM persists the INMEMORY attribute in the data dictionary for the object; the change is not temporary. It will remain until AIM evicts it or a DBA manually alters it.

1. Oracle Database In-Memory Guide, 23c, "Automating In-Memory Column Store Management". This chapter details the functionality of Automatic In-Memory (AIM).

2. Oracle Database Reference, 23c, "INMEMORYAUTOMATICLEVEL". The documentation for the HIGH value states: "enables full automation for the IM column store. The database automatically manages the population and eviction of objects in the IM column store based on their usage patterns."