Oracle
1Z0-052 · Question #175
1Z0-052 Question #175: Real Exam Question with Answer & Explanation
The correct answer is B: Flashing back a transaction. Undo data is required for flashback operations, recovering failed transactions, and providing read-consistent query results, but is not needed when committing a transaction or changing tablespace status.
Managing Undo Data
Question
Which three operations require undo data? (Choose three.)
Options
- ACommitting a transaction
- BFlashing back a transaction
- CRecovering a failed transaction
- DRunning a read-consistent query
- EChanging a tablespace status from READ ONLY to READ WRITE
Explanation
Undo data is required for flashback operations, recovering failed transactions, and providing read-consistent query results, but is not needed when committing a transaction or changing tablespace status.
Common mistakes.
- A. 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.
- E. 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.
Concept tested. Oracle undo data usage scenarios for transactions and queries
Reference. https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/transactions.html
Topics
#undo data usage#flashback transaction#read consistency#failed transaction recovery
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