Which three are true about the FLASHBACK DATABASE feature? (Choose three.)
Which three are true about the FLASHBACK DATABASE feature? (Choose three.)
The FLASHBACK DATABASE feature allows for the database to be reverted to a previous point in time using specific commands. FLASHBACK DATABASE can be performed using SQL*PLUS, making option B correct. It requires that the database be in ARCHIVELOG mode, as the operation relies on archived redo logs in addition to flashback logs, confirming option F. The feature primarily uses FLASHBACK LOGS to rewind the state of the data, but archived redo logs also play a part in completing the process, thus option D is correct. There is no unnecessary logging from read-only queries as that would be inefficient and unnecessary for flashback operations. Hence, options C and A are incorrect. Option E is also incorrect as redo logs are not always generated during a FLASHBACK DATABASE operation when the database is mounted.
B, E, F agree with ObserverPL: 19c docs: Queries do not change data and thus do not contribute to logging activity for Flashback Database. (Not C)
A is wrong - they are never archived B is CORRECT, C is wrong - why queries would have FLASHBACK LOG overhead? only DMLs generate FLASHBACK LOGs D is wrong - according to documentation and my practice some ARCHIVE LOGs are required too E - no idea... F is CORRECT. ... so the only option seems to be BEF
E All logical flashback features except Flashback Drop rely on undo data (https://docs.oracle.com/cd/E15586_01/backup.1111/e10642/rcmflash.htm)
undo generates redo, which in turn generates flashback entry. I don't think it works the other way around
About C The overhead of logging for Flashback Database depends on the mixture of reads and writes in the database workload. When you have a write-intensive workload, the Flashback Database logging overhead is high since it must log all those database changes. Queries do not change data and thus do not contribute to logging activity for Flashback Database.
Well, E is wrong. One prerequisite for FLASHBACK DATABASE is that the database "must be mounted with a current control file". When mounted the redo log files are not online, and redo cannot be written to it. REF: https://docs.oracle.com/en/database/oracle/oracle-database/19/rcmrf/FLASHBACK-DATABASE.html#GUID-584AC79A-40C5-45CA-8C63-DED3BE3A4511 In another point of the documentation, when using SQL*Plus: "Oracle Flashback Database returns your entire database or an entire PDB to a previous state without requiring you to restore files from backup." REF: https://docs.oracle.com/en/database/oracle/oracle-database/19/bradv/user-managed-flashback-dbpitr.html#GUID-2E5F3F62-17ED-472A-ABBD-FAAF107C6852 Going BDF on this one. If this is an actual question we can contact Oracle support after the exam to point this point.
Thats the thing. they dont tell you if you are right or wrong on which questions. (unless you only wrong on few questions which you can *guess* which one you might be wrong based on the topic)
Answer: B,D,F "Flashback Database can only be used if flashback logs are available." "Any remaining changes are recovered using online and archived redo logs if available." https://blogs.oracle.com/maa/post/flashback-database-and-flashback-logs#:~:text=Flashback%20Database%20can%20only%20be,target%20to%20use%20Flashback%20Database.
as per your justification - not ONLY flashback logs are used each time.
B is False: "You can run this command from the RMAN prompt or from within a RUN command." https://docs.oracle.com/en/database/oracle/oracle-database/19/rcmrf/FLASHBACK-DATABASE.html#GUID-584AC79A-40C5-45CA-8C63-DED3BE3A4511
I think B is wrong. RMAN have to be used to flashback datatabase
You are wrong. RMAN can be used for that as well as SQL*Plus do not follow an examples from official documentation because it just an example.
flashback, use archive log: see "Changes between the last flashback log and the target time must be re-created based on the archived redo log. If no automatic channels are allocated for tape and a needed redo log is on tape, then the FLASHBACK DATABASE operation fails."
BEF for me.
BDF Why D? https://docs.oracle.com/en/database/oracle/oracle-database/19/rcmrf/FLASHBACK-DATABASE.html#GUID-584AC79A-40C5-45CA-8C63-DED3BE3A4511:~:text=You%20must%20enable%20flashback%20logging%20before%20the%20target%20time%20for%20flashback%20by%20issuing%20the%20SQL%20statement%20ALTER%20DATABASE%20...%20FLASHBACK%20ON. You must enable flashback logging before the target time for flashback by issuing the SQL statement ALTER DATABASE ... FLASHBACK ON.
Database mounted. SQL> ALTER DATABASE ARCHIVELOG; Database altered. SQL> ALTER DATABASE OPEN; SQL> ALTER DATABASE FLASHBACK ON; ALTER DATABASE FLASHBACK ON * ERROR at line 1: ORA-38706: Cannot turn on FLASHBACK DATABASE logging. ORA-38709: Recovery Area is not enabled. SQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST='/tmp' SCOPE=BOTH; System altered. SQL> ALTER SYSTEM SET DB_RECOVERY_FILE_DEST_SIZE=1G SCOPE=BOTH; System altered. SQL> ALTER DATABASE FLASHBACK ON; Database altered.
Archived redo log files are also used: "RMAN uses flashback logs to undo changes to a point before the target time or SCN. RMAN automatically restores from backup any archived redo log files that are needed and recovers the database to make it consistent"
D: "The database must be mounted, but not open, with a current control file. "
Sure of BEF
I think answer BEF too. B: You can use sqlplus for FLASHBACK DATABASE. https://docs.oracle.com/en/database/oracle/oracle-database/19/sqlrf/FLASHBACK-DATABASE.html#GUID-BE0ACF9A-BC13-4810-B08B-33326440258B
B,E,F per ObserverPL
BCF correct
Can you clarify why do you think that queries generate FLASHBACK LOG? I think it is true FLASHBACK DATA ARCHIVE but it is different feature than FLASHBACK DATABASE.