Infrequent Recovery Situations - Quiz Explanation

The answers you selected are indicated below, along with text that explains the correct answers.

1.	The complete recovery method, recovering a datafile with no backup, can be used in which of the following situations? Please select the best answer.
	A.	The corrupted datafiles belong to the system tablespace and have no backup, but all archived logs exist since the file was created.
	B.	The corrupted datafiles have no backup and all archived logs exist since the file was created.
	C.	The datafiles needing recovery have no backup and some of the archived logs since the creation of these datafiles are damaged.
	D.	The damaged datafile belongs to a rollback segment tablespace and has no backup, but all archived logs exist since the datafile was created.
	The correct answer is B. B is correct because you can perform a complete recovery to a datafile with no backup as long as all archived logs exist since the file was created. A and D are incorrect because this method cannot be applied to any datafiles that belong to either a system or rollback segment tablespace. C is incorrect because the existence of the archived logs since the creation is one of the requirements for using this recovery method.

2.	To check the backup status of all online datafiles, which data dictionary view do you use? Please select the best answer.
	A.	V$BACKUP_DATAFILE
	B.	V$RECOVER_FILE
	C.	V$BACKUP
	D.	V$BACKUP_REDOLOG
	The correct answer is C.C is correct because V$BACKUP displays the backup status of all online datafiles. A is incorrect because V$BACKUP_DATAFILE displays backup datafile and backup control file information. B is incorrect because V$RECOVER_FILE displays the status of files needing media recovery. D is incorrect because V$BACKUP_REDOLOG displays information about archived logs in backup sets.

3.	Which of the following scenarios would require an incomplete recovery rather than a complete recovery? Please select the best answer.
	A.	A datafile from a temporary tablespace is lost, but all archived logs and backups are available.
	B.	A datafile from a read-only tablespace is missing, but a backup is available.
	C.	The database crashes due to a lost redo log file that was not multiplexed and contains uncommitted transactions.
	D.	A user inadvertently dropped a tablespace, but a backup and all archived logs are available since the last backup.
	The correct answer is C.The database crashes due to a lost redo log file that was not multiplexed and contains uncommitted transactions. Explanation: In Oracle 19c, if a non-multiplexed redo log fileis lost and it contained uncommitted transactions, the database may not be able to perform a complete recovery because there is no way to fully reconstruct the lost transactions. Since redo logs store crucial changes before they are written to datafiles, losing them without a backup means some transactions are permanently lost. In such cases, an incomplete recovery (point-in-time recovery)using `RECOVER DATABASE UNTIL TIME` or `RESETLOGS` is necessary to restore the database to a consistent state before the log loss.