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Oracle

1Z0-052 · Question #227

You have a production instance running on your server. UNDO_RETENTION is not long enough to satisfy read-consistency requirements. How do you change the UNDO_RETENTION value?

The correct answer is A. by executing the ALTER SYSTEM .. command. UNDO_RETENTION is a dynamic Oracle initialization parameter that can be modified online using ALTER SYSTEM without requiring any database restart or mount-state changes.

Managing Undo Data

Question

You have a production instance running on your server. UNDO_RETENTION is not long enough to satisfy read-consistency requirements. How do you change the UNDO_RETENTION value?

Options

  • Aby executing the ALTER SYSTEM .. command
  • Bby re-creating the control file with a new value for UNDO_RETENTION
  • Cby executing the ALTER DATABASE.. command in the MOUNT state
  • Dby executing UPDATE.. statement on V$PARAMETER to change the value of

How the community answered

(36 responses)
  • A
    92% (33)
  • B
    6% (2)
  • D
    3% (1)

Why each option

UNDO_RETENTION is a dynamic Oracle initialization parameter that can be modified online using ALTER SYSTEM without requiring any database restart or mount-state changes.

Aby executing the ALTER SYSTEM .. commandCorrect

UNDO_RETENTION is classified as a dynamic parameter in Oracle, meaning ALTER SYSTEM SET UNDO_RETENTION = <value> takes effect immediately for new transactions without shutting down or restarting the instance. This is the standard and supported method to adjust undo retention on a running database.

Bby re-creating the control file with a new value for UNDO_RETENTION

Control files store structural metadata about the database such as datafile locations and log sequence numbers; UNDO_RETENTION is an initialization parameter and is not stored in or configurable via the control file.

Cby executing the ALTER DATABASE.. command in the MOUNT state

UNDO_RETENTION does not require the database to be in MOUNT state; it is a dynamic parameter modifiable while the database is fully open.

Dby executing UPDATE.. statement on V$PARAMETER to change the value of

V$PARAMETER is a dynamic performance view that reflects current parameter values; it is read-only and cannot be modified with DML statements like UPDATE.

Concept tested: Modifying Oracle dynamic initialization parameter UNDO_RETENTION online

Source: https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/UNDO_RETENTION.html

Topics

#UNDO_RETENTION#ALTER SYSTEM#undo management#read consistency

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