Which three are true about block media recovery? (Choose three.)
Which three are true about block media recovery? (Choose three.)
The data file containing the block being recovered remains online during the recovery process, meaning that only the specific blocks being recovered are inaccessible. Flashback Database does not need to be enabled, as it is only an optional feature that can help speed up the recovery process. The block media recovery cannot repair all logical block corruptions, meaning that logical corruption might require alternate recovery methods.
A, C, F By default , RMAN searches the flashback logs for good copies of the blocks, and then searches for the blocks in full or level 0 incremental backups. You could use the EXCLUDE FLASHBACK LOG option to restrict RMAN from searching the flashback logs. (Not B). A, C main features You can perform block recovery only on blocks that are marked corrupt or fail a corruption check (Not D) The target database must run in ARCHIVELOG mode and be open or mounted with a current control file (Not E).
F is false: Block media recovery may not be able to repair all logical block corruptions. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-BBD0093C-AC8D-490C-868C-FB5F83CB0870
ABC correct https://docs.oracle.com/database/121/BRADV/rcmblock.htm#BRADV89782
ABC B is true because, on the prerequisites, oracle told us that we need have flashback database enabled : https://docs.oracle.com/database/121/BRADV/rcmblock.htm#BRADV89785
And in this note say: "Block media recovery may not be able to repair all logical block corruptions" So F is false, because LBC can repair logical corruption, but not always.
Not B Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. If flashback logging is enabled and contains older, uncorrupted versions of the corrupt blocks, then RMAN can use these blocks, possibly speeding up the recovery. flashback is NOT mandatory only >> possibly speeding up the recovery
Agree with you. Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-21EFB177-2AC7-457C-80A0-63B11A80CD0B
I think is ACF
A. TRUE Block media recovery "Enables affected data files to remain online during recovery" https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-83CB3821-DCA8-459E-8038-CBD4D581A225 B. TRUE, Prerequisites for Block Media Recovery: "Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks." https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-C1164158-496C-4D8A-8A06-D343935FC3B9 C. TRUE, Prerequisites for Block Media Recovery: "With block media recovery, only the blocks actually being recovered are unavailable during the recovery." D E F are wrong. F, "Block media recovery may not be able to repair all logical block corruptions." E, OPEN or MOUNTED "The target database for which one or more blocks are to be recovered must be in the OPEN state."
ACD https://docs.oracle.com/database/121/BRADV/rcmblock.htm#BRADV118 Logical corruption The block has a valid checksum, the header and footer match, and so on, but the contents are logically inconsistent. Block media recovery may not be able to repair all logical block corruptions. In these cases, alternate recovery methods, such as tablespace point-in-time recovery, or dropping and re-creating the affected objects, may repair the corruption.
I think answer D is wrong. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-69B1C218-A199-4993-AC71-C87FE0376E32 paragraph 19.1.2: Basic concepts of Block Media Recovery ... hen writes it to disk when the corruption is first encountered. No subsequent read of the block is successful until the block is recovered. You can perform block recovery only on blocks that are marked corrupt or that fail a corruption check....
ACD D - it can.
A - TRUE - only the corrupt block is inaccessable, all others are fine and usable. B - FALSE. If Flashback is enabled, it can speed up recovery. But it is not required. B states "MUST", which is incorrect. Oracle tries to trick people with the use of MUST/MAY.... C - TRUE - the entire issue is that Oracle can't read the block! D - FALSE - you can run a "validate" to check blocks, but you cannot use block recovery to recover something that is not corrupt. E - FALSE - you can do this type of recovery in the MOUNT state. F - TRUE - It is a different process to fix a logical block corruption. So, ACF are correct.
here you go: RMAN> RECOVER DATAFILE 3 BLOCK 10 ; Starting recover at 31-MAR-2022 07:15:49 using channel ORA_DISK_1 starting media recovery media recovery complete, elapsed time: 00:00:00 Finished recover at 31-MAR-2022 07:15:49 uncorrupted block recovery
ABC correct
I think ABC B - Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-21EFB177-2AC7-457C-80A0-63B11A80CD0B:~:text=Flashback%20Database%20must%20be%20enabled%20on%20the%20target%20database%20for%20RMAN%20to%20search%20the%20flashback%20logs%20for%20good%20copies%20of%20corrupt%20blocks. F is not correct - it can but not 100% - Block media recovery may not be able to repair all logical block corruptions. In these cases, alternate recovery methods, such as tablespace point-in-time recovery, or dropping and re-creating the affected objects, may repair the corruption.
This is why I think C is correct - With block media recovery, only the blocks actually being recovered are unavailable during the recovery. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-83CB3821-DCA8-459E-8038-CBD4D581A225:~:text=With%20block%20media%20recovery%2C%20only%20the%20blocks%20actually%20being%20recovered%20are%20unavailable%20during%20the%20recovery.
A, B, C (C is correct not F) after documentation: https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html ...Block media recovery MAY NOT BE ABLE TO REPAIR ALL ...BUT SOME CAN , IT'S NOT EQUAL TO "It cannot repair ... (F)" logical block corruptions... so definetlly F=WRONG ANSWER.
A. and C. - Without block media recovery, if even a single block is corrupt, then you must take the data file offline and restore a backup of the data file. You must apply all redo generated for the data file after the backup was created. The entire file is unavailable until media recovery completes. With block media recovery, only the blocks actually being recovered are unavailable during the recovery. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-83CB3821-DCA8-459E-8038-CBD4D581A225 B. Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-C1164158-496C-4D8A-8A06-D343935FC3B9
https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-C1164158-496C-4D8A-8A06-D343935FC3B9
ACF is the most proper answer
I agree A, C, D
ABC Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/rman-block-media-recovery.html#GUID-C1164158-496C-4D8A-8A06-D343935FC3B9
RMAN> RECOVER DATAFILE 5 BLOCK 13 2> 3> ; Starting recover at 31-MAR-2022 07:14:33 allocated channel: ORA_DISK_1 channel ORA_DISK_1: SID=48 device type=DISK starting media recovery media recovery complete, elapsed time: 00:00:00 Finished recover at 31-MAR-2022 07:14:34 recovering uncorupted block
ACF, I'd say