1Z0-052 · Question #29
You executed the following command to perform a backup of the USERS tablespace: SQL> ALTER TABLESPACE users BEGIN BACKUP; ALTER TABLESPACE users BEGIN BACKUP * ERROR at line 1: ORA-01123: cannot…
The correct answer is B. The database is in NOARCHIVELOG mode. Online tablespace backups require the database to be in ARCHIVELOG mode so Oracle can use redo logs to ensure media recovery consistency. ORA-01123 is thrown specifically when this mode is not enabled.
Question
You executed the following command to perform a backup of the USERS tablespace:
SQL> ALTER TABLESPACE users BEGIN BACKUP; ALTER TABLESPACE users BEGIN BACKUP * ERROR at line 1:
ORA-01123: cannot start online backup; media recovery not enabled What could be the reason for this error?
Options
- AThe MTTR Advisor is disabled.
- BThe database is in NOARCHIVELOG mode.
- CThe tablespace is already in backup mode.
- DThe Flash Recovery Area is not configured.
How the community answered
(25 responses)- A16% (4)
- B72% (18)
- C4% (1)
- D8% (2)
Why each option
Online tablespace backups require the database to be in ARCHIVELOG mode so Oracle can use redo logs to ensure media recovery consistency. ORA-01123 is thrown specifically when this mode is not enabled.
The MTTR Advisor influences checkpoint frequency for crash recovery tuning but has no relation to enabling or disabling online tablespace backups.
Online (hot) backups place a tablespace in backup mode, which requires media recovery to be available. Media recovery depends on archived redo logs, which are only generated when the database runs in ARCHIVELOG mode. When the database is in NOARCHIVELOG mode, Oracle cannot guarantee a consistent recovery from the backup, so it rejects the ALTER TABLESPACE ... BEGIN BACKUP command with ORA-01123.
If the tablespace were already in backup mode, Oracle would return ORA-01151 ('use media recovery to recover block'), not ORA-01123.
The Flash Recovery Area is an optional storage location for backup files; its absence does not prevent initiating an online backup and does not trigger ORA-01123.
Concept tested: Oracle online backup and ARCHIVELOG mode requirement
Source: https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/backing-up-database.html#GUID-C3A8D9C0-1E56-4DD3-B4FA-CF9B9E02E5C5
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