Which of the following are true concerning block media recovery? (Choose all that apply.)
A.
Any gap in archive logs ends the recovery.
B.
If a gap in archive logs is encountered, RMAN will search forward for newer versions of
the blocks that are not corrupt.
C.
Uncorrupted blocks from the flashback logs may be used to speed recovery.
D.
The database can be in NOARCHIVELOG mode.
E.
None of the above.
Explanation:
Overview of Block Media Recovery (link)
Basic Concepts of Block Media Recovery
Whenever block corruption has been automatically detected, you can perform block media
recovery manually with the RECOVER … BLOCK command. By default, RMAN first
searches for good blocks in the real-time query physical standby database, then flashback
logs and then blocks in full or level 0 incremental backups.
Prerequisites for Block Media Recovery (link)The following prerequisites apply to the RECOVER … BLOCK command:
The target database must run in ARCHIVELOG mode and be open or mounted with a
current control file.
If the target database is a standby database, then it must be in a consistent state, recovery
cannot be in session, and the backup must be older than the corrupted file.
The backups of the data files containing the corrupt blocks must be full or level 0 backups
and not proxy copies.
If only proxy copy backups exist, then you can restore them to a nondefault location on disk,
in which case RMAN considers them data file copies and searches them for blocks during
block media recovery.
RMAN can use only archived redo logs for the recovery.
RMAN cannot use level 1 incremental backups. Block media recovery cannot survive a
missing or inaccessible archived redo log, although it can sometimes survive missing redo
records.
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.
The target database must be associated with a real-time query physical standby database
for RMAN to search the database for good copies of corrupt blocks.
Restore Failover (link)
RMAN automatically uses restore failover to skip corrupted or inaccessible backups and look
for usable backups. When a backup is not found, or contains corrupt data, RMAN
automatically looks for another backup from which to restore the desired files.
Weren’t missing archivelogs supposed to be a no no for this type of recovery?
noe is right, correct answers are a and c
A and C are correct:
http://www.aiotestking.com/oracle/which-of-the-following-are-true-concerning-block-media-recovery-2/
For A:Missing Redo During Block Recovery
Like datafile media recovery, block media recovery cannot generally survive a missing or inaccessible archived log, although it will attempt restore failover when looking for usable copies of archived redo log files, as described in “Restore Failover”. Also, block media recovery cannot survive physical redo corruptions that result in checksum failure. However, block media recovery CAN SURVIVE GAPS in the redo stream if the missing or corrupt redo records DO NOT affect the blocks being recovered. Whereas datafile recovery requires an unbroken series of redo changes from the beginning of recovery to the end, block media recovery only requires an unbroken set of redo changes for the blocks being recovered.
For C: 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.
A is incorrect because a gap will not automatically end the recovery, it will search for unaffected block as you said.
B,C are correct.