Which are the prerequisites for performing flashback transactions on your database? (Choose all that apply.)

Lena V.Feb 21, 2026

Correct answers are A, B, and D. Flashback Transaction relies on LogMiner under the hood to reconstruct UNDO_SQL, so supplemental logging must be enabled at the database level (A) and specifically for primary keys (B), because without primary key logging LogMiner cannot reliably identify which rows to back out. C trips people up because undo retention guarantee sounds like it would be required, but Oracle does not list it as a prerequisite for the feature itself, you just need the undo data to still be present in the undo tablespace, and guarantee is one way to help that but it is not a formal requirement. D is straightforward, the user calling the flashback transaction procedure needs EXECUTE on DBMS_FLASHBACK, no grant means no execution, full stop.

Nina C.Feb 2, 2026

Almost marked C, then noticed undo guarantee is not listed as required.

Ingrid P.Feb 14, 2026

The tricky card to write here is the one separating C from A and B, because students conflate "undo data must exist" with "undo retention guarantee must be configured," and those are not the same claim. Supplemental logging at the database level gives the LogMiner machinery enough column data to reconstruct the compensating DML, and the primary-key supplemental log specifically lets the generated undo SQL target the right row without ambiguity. The DBMS_FLASHBACK execute grant is easy to forget because people assume DBA privilege covers it implicitly, but it does not, so that one deserves its own card with the exact grant syntax on the back. My question is this: if supplemental logging is enabled at the database level but you have NOT explicitly enabled it for primary keys, can Flashback Transaction still generate valid undo SQL, or does it fail outright? Thinking through that edge case is what separates the people who have a card for "what does primary-key supplemental logging add specifically" from those who just memorized "enable supplemental log" as a single undifferentiated fact.

Viktor S.Feb 6, 2026

C tempts you. A, B, D. Undo guarantee is nice, not required.

Dervla O.Jan 29, 2026

Going with C on this one and I feel pretty solid about it. Flashback Transaction depends on reading undo data to reconstruct the reverse DML, and if undo retention is not guaranteed the database can overwrite that undo before you ever get to use it, which means the operation fails at runtime rather than at setup. The whole point of configuring undo retention guarantee is to tell the instance to hold that data even under space pressure, and without it you are essentially hoping the undo survives long enough, which is not a configuration, it is a gamble. Every scenario I have walked through where Flashback Transaction silently breaks traces back to undo being reclaimed too early, so the guarantee is not optional, it is the foundation the feature sits on.