A SQL Server 2017+ feature that monitors query performance using Query Store data and automatically applies or reverses execution plan changes to maintain optimal query performance.
- Automatic Plan Correction: Automatic Tuning currently implements Automatic Plan Correction, detecting execution plan regressions and automatically forcing previously better-performing plans without DBA intervention.
- Performance monitoring: When enabled, SQL Server continuously monitors queries for performance degradation caused by new execution plans and automatically reverts affected queries to their last known good plans.
- Azure SQL enhancements: Azure SQL Database extends Automatic Tuning with additional capabilities, including automatic index creation and recommendations for removing unused indexes.
- Configuration options: DBAs can configure Automatic Tuning to operate in recommendation-only mode, where it suggests corrective actions, or automatic mode, where SQL Server applies performance corrections autonomously.
- Role of DBAs: Automatic Tuning addresses a specific category of execution plan regressions but does not replace DBA expertise. More complex performance issues still require detailed investigation and manual optimization.
- Related terms: Query Store, Execution Plan, Parameter Sniffing, Index Rebuild.
