Complete Database Recovery in Oracle - Quiz Explanation

The correct answers are indicated below, along with text that explains the correct answers.
 
1. You are switching a database to ARCHIVELOG mode. Which puts the steps in the correct sequence?
Please select the best answer.
  A. STARTUP MOUNT, ALTER DATABASE ARCHIVELOG, ALTER DATABASE OPEN, SHUTDOWN, make backup
  B. SHUTDOWN, make backup, STARTUP MOUNT, ALTER DATABASE ARCHIVELOG, ALTER DATABASE OPEN
  C. STARTUP, ALTER DATABASE ARCHIVELOG, SHUTDOWN, make backup
  D. SHUTDOWN, STARTUP MOUNT, ALTER DATABASE ARCHIVELOG, make backup, ALTER DATABASE OPEN
  The correct answer is D.
A is incorrect because you have to shut down the database and start it up in mount mode before you perform the switching. B is incorrect because you must make a backup after you switch your database to ARCHIVELOG mode. C is incorrect because you can only perform the switch when the database is in mount mode.

2. Read the following situation and then select the best answer. The system tablespace is contained in one datafile and the datafile becomes corrupt while the database is in ARCHIVELOG mode. A valid online backup of the entire database, including system tablespace datafile, was completed last night. Which is the most appropriate action to take to recover the datafile to the time of corruption?
Please select the best answer.
  A. Restore the datafile from backup and apply all archive logs
  B. Use the ALTER DATABASE ARCHIVELOG command
  C. Restore the entire database from last night's complete backup
  D. Perform a point-in-time recovery
  The correct answer is A.
B is incorrect because this is a command to switch the database to ARCHIVELOG mode. C is incorrect because this will bring the database backup to the time the backup is made, not to the time of corruption. D is incorrect because point-in-time recovery cannot be used to recover to the time of corruption; instead, it only recovers to some point between the last backup and the time of corruption.

3. What files need to be restored in order to make a complete recovery?
Please select the best answer.
  A. All the datafiles, control files, and the parameter file
  B. All the online redo log files
  C. Only lost or damaged datafiles
  D. Only the archived log files
  The correct answer is C.
C is correct because these files are required for a complete database recovery. A is incorrect because you do not need to restore all the datafiles. Restoring control files and the parameter file in the process of complete recovery will bring your database back in time. B is incorrect because the online redo logs should not be restored since they are going to be applied to the restored datafile to roll back your database to the time of the instance failure. D is incorrect because you need to apply the archived log files to the restored datafiles in the process of recovery.

4. When you perform an open database recovery, what must you do before restoring the damaged or lost datafiles?
Please select the best answer.
  A. Shutdown the database by issuing the SHUTDOWN ABORT command
  B. Take the damaged or lost datafile or tablespace offline
  C. Make sure the damaged or lost datafile or tablespace is online
  D. Bring the datafile or tablespace online
  The correct answer is B.
B is correct because you have to take the damaged datafile offline before you restore it. A is incorrect because you only shut down the database if you perform a closed database recovery. C is incorrect because the file must be offline before you restore it. D is incorrect because you have to bring the restored datafile or tablespace online after the recovery is finished.