CompTIA DataSys+ (DS0-001)Database Management and MaintenanceEasy
A database administrator is configuring monitoring for a new critical production database. They want to track a metric that indicates how frequently the database system needs to read data from disk rather than finding it in memory. Which metric should they prioritize monitoring?
- ANetwork Latency
- BCPU Utilization
- CBuffer Cache Hit Ratio
- DActive Sessions
Show answer & explanationAnswer & explanation
Correct answer: C. Buffer Cache Hit Ratio
Buffer Cache Hit Ratio directly indicates how often data requests are fulfilled from the in-memory buffer cache versus requiring a slower disk I/O operation. A low ratio suggests frequent disk reads and potential I/O bottlenecks.
Why the other options are wrong
- A. Network latency measures communication delay, not disk vs. memory access.
- B. CPU utilization measures processor load, not directly how often data is read from disk vs. memory.
- D. Active sessions indicate concurrent user activity, not the efficiency of data retrieval from storage.
Buffer Cache Hit Ratio
A performance metric indicating the percentage of data requests that were satisfied from the database's in-memory cache rather than from slower disk storage.
- Higher ratio means fewer disk I/O operations.
- A low ratio indicates potential memory shortage or inefficient queries.
- Optimal ratios vary by database system and workload (often 90%+).
Memory trick: Buffer hit ratio: how often you 'hit' the fast memory.