Diag: W10 parameter churn detection (unstable configuration)

[nanoDBA]

Problem

Key parameters change frequently (every 1-2 runs) without clear pattern, indicating reactive tuning rather than stable strategy. Trend analysis becomes unreliable because metrics shift from config changes, not actual improvements.

Suggested Fix

For key parameters (@TimeLimit, @ModificationThreshold, @SortOrder, @QueryStorePriority, @StatsInParallel), flag when values change in >60% of recent runs. Show change frequency and recommend stabilizing for 10+ runs before adjusting.

Example Output

"Parameter volatility: @Timelimit changed 4 times in 6 runs (3600->7200->3600->5400). @ModificationThreshold changed 3 times. Trend metrics unreliable. Stabilize for 10+ runs before adjusting."

File

sp_StatUpdate_Diag.sql, new check W10 (PARAMETER_CHURN)

[nanoDBA]

Fixed in diag v2026.03.26 -- W10 PARAMETER_CHURN check. Detects when 2+ key parameters have 3+ distinct values across 5+ runs, indicating reactive tuning.