Which tablespaces are mandatory in an Oracle database for it to be operational? (Choose all that apply.)

An undo tablespace is required for DML operations and read consistency, but the database can technically open in restricted mode without one, so it is not a hard requirement for the database to be operational.

The USERS tablespace is only a conventional default destination for user-created objects and has no role in Oracle's internal engine startup or operation.

SYSAUX was introduced in Oracle 10g as a mandatory auxiliary tablespace that offloads many built-in Oracle components - such as AWR, the Scheduler, and XML DB - from the SYSTEM tablespace to reduce contention. The database cannot be created, mounted, or opened without SYSAUX present. Its absence causes Oracle to refuse to open the database entirely.

The SYSTEM tablespace is the most critical tablespace in an Oracle database because it houses the data dictionary, which stores all metadata about database objects, users, privileges, and structures. Without the SYSTEM tablespace, the Oracle instance cannot mount or open, as every internal operation depends on reading this metadata. It is a hard requirement with no workaround.

A temporary tablespace is needed for sort and hash operations that spill to disk, but its absence does not prevent the database from opening; only certain session operations would fail.