Which two statements are true regarding undo tablespaces? (Choose two.)

The correct answer is A. The database can have more than one undo tablespace C. Undo segments automatically grow and shrink as needed, acting as circular storage buffer for their. Oracle databases support multiple undo tablespaces simultaneously, and undo segments use a circular buffer mechanism that grows and shrinks automatically to manage undo data.

Managing Undo Data

Question

Options

AThe database can have more than one undo tablespace
BThe UNDO_TABLESPACE parameter is valid in both automatic and manual undo management
CUndo segments automatically grow and shrink as needed, acting as circular storage buffer for their
DAn undo tablespace is automatically created if the UNDO_TABLESPACE parameter is not set and

How the community answered

(56 responses)

A
88% (49)
B
7% (4)
D
5% (3)

Why each option

Oracle databases support multiple undo tablespaces simultaneously, and undo segments use a circular buffer mechanism that grows and shrinks automatically to manage undo data.

AThe database can have more than one undo tablespaceCorrect

Oracle allows multiple undo tablespaces to exist within a single database instance. Although only one undo tablespace can be active at a time (designated by the UNDO_TABLESPACE parameter), additional undo tablespaces can be created and the active one switched as needed for maintenance or space management.

BThe UNDO_TABLESPACE parameter is valid in both automatic and manual undo management

The UNDO_TABLESPACE initialization parameter is only recognized under Automatic Undo Management (AUM); in manual undo management mode, rollback segments are used instead and this parameter is ignored.

CUndo segments automatically grow and shrink as needed, acting as circular storage buffer for theirCorrect

Undo segments within an undo tablespace operate as a circular storage buffer, reusing extents in a wrap-around fashion once undo data is no longer needed for active transactions or read consistency. They automatically extend when demand increases and shrink when undo retention requirements are satisfied.

DAn undo tablespace is automatically created if the UNDO_TABLESPACE parameter is not set and

An undo tablespace is not automatically created simply because the UNDO_TABLESPACE parameter is omitted; it must be explicitly created via DDL or specified during database creation with the UNDO TABLESPACE clause.

Concept tested: Oracle Automatic Undo Management and undo tablespace behavior

Source: https://docs.oracle.com/en/database/oracle/oracle-database/19/admin/managing-undo.html

Topics

#undo tablespace#automatic undo management#undo segments#circular buffer

Community Discussion

Orla P.Jan 7, 2026

The correct answers are A and C, and here is why they hold up. A is correct because Oracle absolutely allows you to create more than one undo tablespace in a database, even though only one can be active for an instance at any given time. You might have a second one ready for a maintenance switch or for a different instance in a RAC environment, so the design intentionally supports multiple. C is correct because under automatic undo management, Oracle handles undo segment sizing without your intervention, and those segments wrap around in a circular fashion, overwriting older undo data once it is no longer needed for read consistency or rollback. B trips up a lot of candidates because the UNDO_TABLESPACE parameter only applies when UNDO_MANAGEMENT is set to AUTO. In manual mode you are working with rollback segments directly and that parameter is simply not in play. D is a distractor built around a half-truth about database creation defaults, but it does not describe a reliable or accurate rule you can depend on for the exam. Lock in A and C and move on.

Brenda K.Jan 9, 2026

Solid breakdown, Orla, and I will add one clock-saving flag for test day: if you see any answer choice claiming undo segments behave like traditional rollback segments under AUTO mode, kill it fast, because that confusion between manual and automatic management is exactly how the exam burns candidates who second-guess A and C.

Brenda K.Jan 17, 2026

Quick win here, do not overthink it. A is a gimme because Oracle absolutely lets you have multiple undo tablespaces sitting around even though only one is active per instance at a time, and C describes the classic circular buffer behavior you see in every Oracle fundamentals chapter. Here is what I want you to think through before the real exam: if you already know C is true, can you explain exactly what happens to an undo segment when a transaction commits but a long-running query still needs that old data for read consistency?

Prof. SaraDec 30, 2025

A and C nail it. Multiple undo tablespaces allowed, segments self-manage like a ring buffer.

Orla P.Jan 2, 2026

Worth flagging for exam day: you can have multiple undo tablespaces created, but only one is active per instance at a time, and that distinction shows up in trick answers fairly often on the OCP.

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