OCP 1Z0 052 26

26. 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.

Answer: AC

A 可以有多个undo tablespace，但一次只会用一个

If the database contains multiple undo tablespaces, you can optionally specify at startup that you want to use a specific undo tablespace. This is done by setting the UNDO_TABLESPACE initialization parameter

B The database can also run in manual undo management mode. In this mode, undo space is managed through rollback segments, and no undo tablespace is used.

此时 UNDO_TABLESPACE 没用。

C With automatic undo management, the database manages undo segments in an undo tablespace

D An auto-extending undo tablespace named UNDOTBS1 is automatically created when you create the database with Database Configuration Assistant (DBCA).

在安装时会自动建一个UNDOTBS1 ，但不是在实例启动时。

If no undo tablespace is available, the instance starts without an undo tablespace and stores undo records in the SYSTEM tablespace.