Which three operations require undo data? (Choose three.)

Committing a transaction makes changes permanent by writing redo data to the redo log - it does not require undo data because there is nothing to roll back after a commit.

Flashing back a transaction uses undo data to reconstruct prior versions of modified rows, allowing Oracle to reverse committed changes to a previous point in time. Without undo data retained in the undo tablespace, the Flashback Transaction feature cannot operate.

Recovering a failed transaction requires undo data to roll back any uncommitted changes that were made before the failure occurred, restoring the affected data blocks to their pre-transaction state.

Read-consistent queries rely on undo data to build a consistent snapshot of the data as it existed at the query's start SCN, allowing readers to see a stable view even when other sessions are concurrently modifying the same rows.

Changing a tablespace status from READ ONLY to READ WRITE is a DDL operation that updates the control file and data file headers and does not involve undoing any row-level data changes.