You notice a performance change in your production Oracle 12c database. You want to know which change caused this performance difference. Which method or feature should you use?

Question

Options

• ACompare Period ADDM report
• BAWR Compare Period report
• CActive Session History (ASH) report
• DTaking a new snapshot and comparing it with a preserved snapshot.

• A
  3% (1)
• B
  84% (32)
• C
  8% (3)
• D
  5% (2)

Explanation

AWR Compare Period report is correct because it is Oracle's purpose-built tool for comparing two distinct time periods side-by-side, surfacing differences in wait events, SQL performance, resource consumption, and system statistics - precisely what you need to pinpoint what changed between a healthy and degraded period.

Why the distractors are wrong:

• A (Compare Period ADDM): ADDM's compare period feature exists but delivers high-level findings and recommendations, not the granular metric-by-metric breakdown needed to identify the root cause of a specific change.
• C (ASH report): ASH captures sampled session activity and is ideal for diagnosing recent or in-progress performance issues, but it is not designed for structured period-over-period comparison and lacks long-term retention.
• D (New snapshot vs. preserved snapshot): This describes the manual underlying mechanism - AWR already does this automatically and formats it as the Compare Period report. Describing the process doesn't name the correct Oracle feature.

Memory tip: Think of AWR Compare as a "before and after X-ray" - it shows the full picture of two time periods side by side. When the question asks what changed between periods, reach for AWR Compare. When it asks what's happening right now, reach for ASH.

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