fabric-onelake-perf-remediatelisted

# OneLake Performance remediate Systematic diagnostic and remediation toolkit for Microsoft Fabric OneLake performance issues. Covers the full stack from capacity-level throttling down to individual Delta table file layout problems. ## When to Use This Skill - OneLake read or write operations are slow or timing out - Lakehouse or warehouse queries have unexpectedly high latency - Spark jobs are being throttled with HTTP 430 errors - Delta tables have accumulated many small files (small file problem) - Direct Lake semantic models are falling back to DirectQuery - Cold cache performance is significantly slower than warm cache - Cross-region data access is adding network latency - V-Order is not applied or needs to be enabled/disabled - Table maintenance (OPTIMIZE, VACUUM) is failing or not improving performance - Capacity utilization is high and jobs are queuing ## Prerequisites - Microsoft Fabric workspace with Contributor or higher role - Access to the Monitoring Hub in the Fabric portal - PowerShell 7+ with Az.Fabric module (for automation scripts) - Familiarity with Spark SQL or T-SQL for diagnostic queries ## Diagnostic Decision Tree Follow this sequence to isolate the root cause: ``` 1. Is the issue capacity-level? → Check Spark VCore utilization and queue depth 2. Is the issue cold cache? → Check data_scanned_remote_storage_mb 3. Is the issue file layout? → Check small file count and V-Order status 4. Is the issue cross-region? → Verify data and capacity are co-l