Read Only Backups - Quiz Explanation
The correct answers are indicated below, along with the text that explains the correct answers.
1.
What is the advantage of the NOLOGGING option for a table, index or partition?
Please select the best answer.
A.
No redo is generated for INSERTS, UPDATES, or DELETES occurring on the affected object(s)
B.
No log switches occur during INSERTS
C.
No redo is generated during direct-load INSERT operations occurring on the affected object(s)
D.
No archive logs are created
The correct answer is C.
C is correct because no redo information is generated when you set the affected objects in nologging mode and perform direct-load insert. A is incorrect because UPDATES and DELETES are always logged. B is incorrect because log switches can occur at any time. D is incorrect because archive logs will always be created when in ARCHIVELOG mode.
2.
Which of the following database file(s) are affected by ALTER TABLESPACE <tablespace> READ ONLY?
Please select the best answer.
A.
The control file
B.
DBWR
C.
Files belonging to tablespace SYSTEM
D.
LGWR
The correct answer is A.
A is correct because any changes you make to a tablespace are going to be recorded in the control file. B and D are incorrect because they are not database files. C is incorrect because read-only status is stored in the control file, not in the file headers of the tablespace SYSTEM.
3.
Which statement correctly describes an attribute of Oracle read-only backups?
Please select
the best answer
.
A.
Oracle read-only backups can be performed while the database is open and require the database to be in ARCHIVELOG mode.
B.
Oracle read-only backups allow updates to the data files during the backup process to ensure the most current data is captured.
C.
Oracle read-only backups can only be accomplished through RMAN (Recovery Manager) with the database in NOARCHIVELOG mode.
D.
Oracle read-only backups require the database instance to be shut down before the backup can commence.
The correct answer is A.
An Oracle read-only backup refers to the process of backing up the database while it is still open and accessible to users for read operations, but no write operations are permitted on the datafiles during the backup. This is a viable strategy when the database can be made read-only for the duration of the backup due to minimal impact on read operations. The key requirement for this process to be effective and to ensure data integrity is that the database must be running in ARCHIVELOG mode. This mode enables the Oracle database to archive filled online redo log files, which is essential for performing consistent backups and point-in-time recovery of the database. It ensures that all changes made to the database are preserved in an archive to be applied after the backup, bringing the database to a consistent state.
The other options provided are incorrect: B is Incorrect, because during a read-only backup, data files are not updated; the idea is to freeze the state of the database for the backup process. C is Incorrect, because backups with RMAN can be performed whether the database is in ARCHIVELOG mode or NOARCHIVELOG mode; the latter does not allow for point-in-time recovery and is generally not recommended for production databases. D is Incorrect, because the whole premise of a read-only backup is that it can be performed while the database is open; shutting down the database would lead to a cold backup, not a read-only backup.
