In which three scenarios is media recovery required?
A.
when a tablespace is accidentally dropped from a database
B.
when archived redo log files are lost
C.
when data files are lost
D.
when one of the online redo log members is corrupted
E.
when all control files are lost
Explanation:
Reference:
http://docs.oracle.com/cd/A87860_01/doc/server.817/a76993/recoscen.htm
How is C not a correct answer (if the key is right)? That would imply that one of the other answers is wrong.
ACE would appear to be a better answer. I’m not sure about D being correct. I will have to research this.
A C E
ACE
Why not D? Cause they say it’s only one member of the online redo log members, not ALL.
Recovering After Losing a Member of a Multiplexed Online Redo Log Group
If the online redo log of a database is multiplexed, and at least one member of each online redo log group is not affected by the media failure, Oracle allows the database to continue functioning as normal. Oracle writes error messages to the LGWR trace file and the alert.log of the database.
Solve the problem by taking one of the following actions:
If the hardware problem is temporary, then correct it. LGWR accesses the previously unavailable online redo log files as if the problem never existed.
If the hardware problem is permanent, then drop the damaged member and add a new member using the procedure below.
Note:
The newly added member provides no redundancy until the log group is reused.
To replace a damaged member of a redo log group:
Locate the filename of the damaged member in V$LOGFILE. The status is INVALID if the file is inaccessible:
SELECT group#, status, member FROM v$logfile;
GROUP# STATUS MEMBER
——- ———– ———————
0001 /oracle/dbs/log1a.f
0001 /oracle/dbs/log1b.f
0002 /oracle/dbs/log2a.f
0002 INVALID /oracle/dbs/log2b.f
0003 /oracle/dbs/log3a.f
0003 /oracle/dbs/log3b.f
Drop the damaged member. For example, to drop member log2b.f from group 2, issue:
ALTER DATABASE DROP LOGFILE MEMBER ‘/oracle/dbs/log2b.f’;
Add a new member to the group. For example, to add log2c.f to group 2, issue:
ALTER DATABASE ADD LOGFILE MEMBER ‘/oracle/dbs/log2c.f’ TO GROUP 2;
If the file you want to add already exists, then it must be the same size as the other group members, and you must specify REUSE:
ALTER DATABASE ADD LOGFILE MEMBER ‘/oracle/dbs/log2b.f’ REUSE TO GROUP 2;
Recovering After the Loss of All Members of an Online Redo Log Group
If a media failure damages all members of an online redo log group, different scenarios can occur, depending on the type of online redo log group affected by the failure and the archiving mode of the database.
If the damaged log group is inactive, then it is not needed for instance recovery; if it is active, then it is needed for instance recovery.
If the group is… Then… And you should…
Inactive
It is not needed for instance recovery
Clear the archived or unarchived group.
Active
It is needed for instance recovery
Attempt to issue a checkpoint and clear the log; if impossible, then you must restore a backup and perform incomplete recovery up to the most recent available log.
Current
It is the log that Oracle is currently writing to
Attempt to clear the log; if impossible, then you must restore a backup and perform incomplete recovery up to the most recent available log.
ACE
ACE
ACE A is equal to C so whether you choose both or None!
based on the http://docs.oracle.com/cd/A87860_01/doc/server.817/a76993/recoscen.htm#11724.
the right answer is A C E, because says If the damaged log group is inactive, then it is not needed for instance recovery; if it is active, then it is needed for instance recovery.
ACE