Snowflake SnowPro Core

Explanation

Let's analyze each statement about the ARIES algorithm:

1. "The application of the REDO operation is restricted to committed transactions." - FALSE (F)

   • In ARIES, REDO operations are applied to all transactions (both committed and uncommitted) to restore the database to the state just before the crash. This is because ARIES uses a repeating history approach where it replays all logged operations regardless of transaction commit status.

2. "A steal/no-force approach is used for the rules that govern when a database cache page can be written to disk." - TRUE (V)

   • ARIES uses a steal/no-force policy:
     • Steal: Allows uncommitted transaction pages to be written to disk (dirty pages can be flushed)
     • No-force: Does not require committed transaction pages to be written to disk immediately
   • This approach provides better performance compared to force/steal or force/no-steal policies.

3. "UNDO operations are logged to avoid repeating completed UNDO operations if a failure occurs during the recovery process." - TRUE (V)

   • ARIES uses compensation log records (CLRs) to log UNDO operations. If a crash occurs during recovery, these CLRs prevent redoing UNDO operations that have already been completed, ensuring idempotence.

4. "The Transaction Table contains an entry for each dirty page in the cache, which includes the page identifier and the log sequence number of the oldest update to that page." - FALSE (F)

   • This description actually refers to the Dirty Page Table (DPT), not the Transaction Table. The Transaction Table tracks active transactions (transaction ID, status, last LSN), while the Dirty Page Table tracks dirty pages in the buffer pool with their recLSN (recovery LSN).

Correct sequence: F – V – V – F

Answer: A