Answer: Cache hit percentage

## Analysis of the Performance Issue The scenario describes a specific performance pattern where: - **Commonly used queries** are experiencing slow performance - **Infrequently used queries** show no performance degradation - This pattern suggests the issue is related to query caching mechanisms ## Metric Analysis ### **B: Cache hit percentage** - **CORRECT** - Cache hit percentage measures how often queries are served from the result set cache rather than being executed against the underlying data - Low cache hit percentage for commonly used queries indicates they are not being cached effectively, forcing repeated execution against the data warehouse - This directly explains why frequently run queries are slow while infrequent queries (which wouldn't benefit from caching anyway) perform normally - Monitoring this metric helps identify cache inefficiencies and determine if cache warming or query optimization is needed ### **A: DWU limit** - **INCORRECT** - DWU (Data Warehouse Unit) limit monitoring shows overall resource consumption - This would affect all queries uniformly, not just commonly used ones - The selective nature of the performance issue makes this unlikely ### **C: Local tempdb percentage** - **INCORRECT** - Local tempdb usage relates to temporary storage for query operations - This metric would impact complex queries requiring significant temporary storage, not specifically commonly used queries - The pattern described doesn't align with tempdb-related issues ### **D: Data IO percentage** - **INCORRECT** - Data IO percentage measures read/write operations to storage - While important for overall performance, this would affect all queries accessing data - The selective impact on commonly used queries suggests a caching issue rather than general IO constraints ## Recommended Action Monitoring cache hit percentage will help identify if the result set cache is functioning optimally. If cache hit percentage is low for commonly used queries, consider implementing cache warming strategies or reviewing query patterns to improve cache utilization.

Author: LeetQuiz Editorial Team