Which two are true about instance recovery? (Choose two.)
A.
It is not possible if an archived log is missing.
B.
It is performed automatically after the database is opened; however, blocks requiring recovery are not available until they are recovered.
C.
Setting FAST_START_MTTR_TARGET to a lower value reduces instance recovery time by causing dirty buffers to be written to disk more frequently, thereby reducing the number of I/Os needed during instance recovery.
D.
It is performed by the Recovery Writer (RVWR) background process.
E.
Setting FAST_START_MTTR_TARGET to a higher value reduces instance recovery time by causing the log writer to write more frequently, thereby reducing the number of I/Os needed during instance recovery.
F.
It is performed automatically while the database remains in MOUNT state. Then the database is opened.
well i'm not so sure about it:
You are right about the instance recovery begins after "alter database open" is executed but that doesn't mean that the database is already open when the recovery starts.
The instance recovery is executed in 2 steps, rollforward and rollback and the database is open just after the rollforward is completed.
So i think that is not accuracy to tell that the instance recovery is performed after the database is open.
What do you thik?
Here is a good diagram to understand it.
https://www.orskl.com/how-oracle-database-does-instance-recovery-after-failures/
Answer is CF:
F: instance recovery happens at mount state.
from the student guide = ... The instance mounts the control files and then ATTEMPTS to open the datafiles. when it realizes the datafiles have not been synchronized during shutdown .....
B would have been correct if the word STARTED was used instead of OPENED.
Oracle Database performs instance recovery automatically in the following situations:
The database opens for the first time after the failure of a single-instance database or all instances of an Oracle RAC database. This form of instance recovery is also called crash recovery. Oracle Database recovers the online redo threads of the terminated instances together.
https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/oracle-database-instance.html#GUID-6F20EBD4-CD7A-41BA-823B-BB3B25C7C99E
According to the documentation, B and C are true
This is quite a poorly formed question in my mind, instance recovery starts when you 'startup' the database, not when it opens. If you run a shutdown abort you can clearly see in the alert log that the application of redo logs starts when the database is mounted after running the startup command and then the database is opened after it confirms that the undo tablespace is available. Then the undo is applied to rollback the database to a consistent state it was in before the unclean shutdown. So C is definitely true but B and F are both technically false as they ignore that Instance Recovery has two phases. Not sure if the Q is wrong on here but I would say that F is more true as IR starts when the DB is mounted, but it opens when rollforward is done, not when IR is completed.
It think it was release 8 when the faster start was introduced by opening the instance BEFORE the recovery is complete. However, the recovered blocks remain unavailable until the recovery is done.
For me it's BC.
https://docs.oracle.com/cd/E25178_01/server.1111/e25789/startup.htm
Oracle Database performs instance recovery automatically in the following situations:
The database opens for the first time after the failure of a single-instance database or all instances of an Oracle RAC database.
For me F is totally wrong. As others said the Instance recovery is performed in 2 steps , the first one is the rolling forward that needs Online Redo Logs to execute. Online Redo Logs are available just after database id open because in Mount state just control files are opened. So for me Correct answers are B & C
nono, redo are applied after db is open in instance recovery. See this (the docs is for release 21, but it is the same for 19... and 12, and 11, and 10 and 9 and 8 and i'm not sure for 7 - i never covered 7) Figure 15-6 https://docs.oracle.com/en/database/oracle/oracle-database/21/cncpt/oracle-database-instance.html#GUID-728C6BE1-5687-4DC5-B570-D2042C88F935
BC is correct.
wow. most of you are wrong.
instance must be open to get undo segment online. without that, oracle doesn't know the undo data to recover the (not commited) transactions. so the phrase "remains in MOUNT state" is definitively wrong.
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