1Z0-078 practice question 15 of 15

Which three statements are true about undo management in a RAC environment? (Choose three.)

Answer options

A: You can dynamically assign a newly created undo tablespace to an instance. Correct answer

B: In a policy-managed RAC database, an undo tablespace may automatically be created if OMF is enabled for the database. Correct answer

C: An instance that performs instance recovery can write to the undo tablespace of a failed instance. Correct answer

D: A mixture of automatic undo management and manual undo management is supported within a RAC database.

E: It is necessary to assign a specific undo tablespace to a specific instance.

Correct Answer:

A. You can dynamically assign a newly created undo tablespace to an instance.; B. In a policy-managed RAC database, an undo tablespace may automatically be created if OMF is enabled for the database.; C. An instance that performs instance recovery can write to the undo tablespace of a failed instance.

Explanation

In RAC, Automatic Undo Management (AUM) lets each instance use its own undo tablespace, but you can change that association online with ALTER SYSTEM. When a policy-managed instance starts and no undo is assigned, Oracle automatically creates and assigns one if OMF is enabled. During instance recovery, the surviving instance updates (reads and writes) the undo segments that belonged to the failed instance to complete transaction recovery. Mixing AUM with manual undo is disallowed and explicit assignment is optional, not mandatory.

Why Incorrect

D. All RAC instances must run in the same undo mode; mixing automatic and manual is unsupported.
E. Oracle automatically selects an undo tablespace if none is specified, so explicit assignment is not required.

References

1. Oracle Database Administrator’s Guide 19c, ch. “Managing Undo Data in a RAC Environment”, Sec. “Creating and Assigning Undo Tablespaces” (E96338-15), para. 3-4.

2. Oracle Database Administrator’s Guide 19c, same chapter, “Automatic Undo Tablespace Creation with OMF”, para. 1.

3. Oracle Database Administrator’s Guide 19c, same chapter, “Instance Recovery and Undo”, para. 2.

4. Oracle Database Administrator’s Guide 19c, “Restrictions on Mixed Undo Modes”, para. 1.

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