Which statement about recovering from the loss of a redo log group is true?
A.
If the lost redo log group is ACTIVE, you should first attempt to clear the log file.
B.
If the lost redo log group is CURRENT, you must clear the log file.
C.
If the lost redo log group is ACTIVE, you must restore, perform cancel-based incomplete recovery, and open the database using the RESETLOGS option.
D.
If the lost redo log group is CURRENT, you must restore, perform cancel-based incomplete recovery, and open the database using the RESETLOGS option.
Explanation:
If the lost redo log group is CURRENT, you must restore, perform cancel-based incomplete recovery, and open the database using the RESETLOGS option. A redo log group with a CURRENT status indicates that LGWR is currently writing to it. To recover from this failure, you must restore the database from a whole backup and perform cancel-based incomplete recovery. Then, you should open the database using the RESETLOGS option.
The option that states if the lost redo log group is ACTIVE, you should first attempt to clear the log file is incorrect. If the lost redo log group has a status of ACTIVE, it is needed for instance recovery. In that situation, you should first attempt to perform a checkpoint. After the checkpoint, the log file is no longer required for instance recovery.
The option that states if the lost redo log group is CURRENT, you must clear the log file is incorrect. You would clear the log file only if the status of the lost redo log group was INACTIVE. After clearing the log file, the log file may be reused.
The option that states if the lost redo log group is ACTIVE, you must restore, perform cancel-based incomplete recovery, and open the database using the RESETLOGS option. These actions are only necessary if the log file has a CURRENT status, which indicates LGWR is currently writing to it.
In question 106 I can see that:
– online redo log file of the current redo group is corrupted.
and the answer is
ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP 1;
Here, in the explanation of the answer I can see that if the lost redo log is CURRENT then is needed to restore, perform cancel-based incomplete recovery, and open the database using the RESETLOGS option.
What is the difference between the situation described in 106 and 107 questions?
in 106 Redo log Group state may be Active not Current. But in 107 redo log group status is Current.
in the question 106 is written:
“You discover that the online redo log file of the current redo group is corrupted.”
So it is current rego group not active.
It all depends on how you receive the error ORA-00313
– If you get it on a normal startup (i.e. problem occurred when the database was turned off) then the answer is
mount the database
ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP x;
and then do a backup
-if the database crashes (i.e. problem occurred when the database was on) and you get this error during the instance recovery then you need to
do a database point in time recovery of the whole (or use FLASHBACK)
and then do a backup