Which two statements are true regarding undo tablespaces? (Choose two.)
A.
The database can have more than one undo tablespace
B.
The UNDO_TABLESPACE parameter is valid in both automatic and manual undo management
C.
Undo segments automatically grow and shrink as needed, acting as circular storage buffer for
their assigned transactions
D.
An undo tablespace is automatically created if the UNDO_TABLESPACE parameter is not set and
the UNDO_MANAGEMENT parameter is set to AUTO during the database instance start up
Yes A and C
UNDO_MANAGEMENT (static init) AUTO is the default, enables AUM. Don’t set it to MANUAL.
UNDO_TABLESPACE Use this only when the database has multiple undo tablespaces and you want to use a particular one. In RAC every instance has its own undo tablespace and its own UNDO_TABLESPACE (init)
UNDO_TABLESPACE specifies the undo tablespace to be used when an instance starts up. If this parameter is specified when the instance is in manual undo management mode, then an error will occur and startup will fail.
If the UNDO_TABLESPACE parameter is omitted, the first available undo tablespace in the database is chosen. If no undo tablespace is available, the instance will start without an undo tablespace. In such cases, user transactions will be executed using the SYSTEM rollback segment. You should avoid running in this mode under normal circumstances.
You can replace an undo tablespace with another undo tablespace while the instance is running.
C: the original segment can automatically grow and shrink as needed, it acts as a cycle storage buffer allocated transaction.
D: incorrect. It is automatically created by DBCA, or manually created by the create database or create undo tablespace .