Azure SQL Database Optimization
Platform-specific optimization for Azure SQL Database.
Quick Reference Service Tier Comparison Tier Best For Max Size Key Features Basic Dev/test, light workloads 2 GB Low cost Standard General workloads 1 TB S0-S12 DTUs Premium High I/O, low latency 4 TB P1-P15 DTUs General Purpose (vCore) Most workloads 16 TB Serverless option Business Critical High availability 4 TB In-memory, read replicas Hyperscale Large databases 100 TB Auto-scaling storage DTU vs vCore Aspect DTU vCore Pricing Bundled resources Separate compute/storage Control Limited Fine-grained Reserved capacity No Yes (up to 72% savings) Serverless No Yes (General Purpose) Best for Simple workloads Predictable, migrated workloads Performance Monitoring Resource Consumption -- Last 15 minutes (avg 15-second intervals) SELECT end_time, avg_cpu_percent, avg_data_io_percent, avg_log_write_percent, avg_memory_usage_percent, max_worker_percent, max_session_percent FROM sys.dm_db_resource_stats ORDER BY end_time DESC;
-- Historical (last 14 days, hourly) SELECT start_time, end_time, avg_cpu_percent, avg_data_io_percent, avg_log_write_percent FROM sys.resource_stats WHERE database_name = DB_NAME() ORDER BY start_time DESC;
Query Performance Insight -- Top CPU consumers last hour SELECT TOP 20 qt.query_sql_text, rs.avg_cpu_time / 1000 AS avg_cpu_ms, rs.count_executions, rs.avg_cpu_time * rs.count_executions / 1000 AS total_cpu_ms FROM sys.query_store_query q JOIN sys.query_store_query_text qt ON q.query_text_id = qt.query_text_id JOIN sys.query_store_plan p ON q.query_id = p.query_id JOIN sys.query_store_runtime_stats rs ON p.plan_id = rs.plan_id JOIN sys.query_store_runtime_stats_interval rsi ON rs.runtime_stats_interval_id = rsi.runtime_stats_interval_id WHERE rsi.start_time >= DATEADD(hour, -1, GETUTCDATE()) ORDER BY rs.avg_cpu_time * rs.count_executions DESC;
Automatic Tuning Enable Automatic Tuning -- Enable all auto-tuning options ALTER DATABASE current SET AUTOMATIC_TUNING ( FORCE_LAST_GOOD_PLAN = ON, CREATE_INDEX = ON, DROP_INDEX = ON );
-- Check current settings SELECT * FROM sys.database_automatic_tuning_options;
View Tuning Recommendations -- Current recommendations SELECT name, reason, score, state_desc, is_revertable_action, is_executable_action, details FROM sys.dm_db_tuning_recommendations;
Apply Recommendations -- Force a specific query plan EXEC sp_query_store_force_plan @query_id = 12345, @plan_id = 67890;
-- Unforce plan EXEC sp_query_store_unforce_plan @query_id = 12345, @plan_id = 67890;
Hyperscale Features Storage Auto-Scaling Automatically grows up to 128 TB No need to pre-provision storage Pay only for storage used Read Scale-Out -- Connection string option ApplicationIntent=ReadOnly
-- In application code "Server=myserver.database.windows.net;Database=mydb;ApplicationIntent=ReadOnly;..."
Named Replicas -- Create named replica ALTER DATABASE MyDatabase ADD SECONDARY ON SERVER MySecondaryServer WITH (SERVICE_OBJECTIVE = 'HS_Gen5_2', SECONDARY_TYPE = Named, NAME = N'MyReadReplica');
Serverless Configuration Configure Auto-Pause -- Via Azure Portal, CLI, or PowerShell -- Set auto-pause delay (minutes), min/max vCores
-- Check current usage SELECT cpu_percent, auto_pause_delay_in_minutes_configured FROM sys.dm_db_resource_stats_serverless;
Serverless Best Practices Use for intermittent workloads - Saves cost during idle periods Set appropriate min vCores - Prevents cold starts for time-sensitive apps Monitor auto-pause - Auto-resume adds latency Consider always-on for consistent workloads - Provisioned may be cheaper Connection Optimization Connection Pooling // .NET connection string "Server=tcp:myserver.database.windows.net,1433;Database=mydb; Min Pool Size=10;Max Pool Size=100;Connection Timeout=30;"
Retry Logic // Azure SQL requires retry logic for transient faults var options = new SqlRetryLogicOption() { NumberOfTries = 5, DeltaTime = TimeSpan.FromSeconds(1), MaxTimeInterval = TimeSpan.FromSeconds(30) };
Connection Best Practices Use connection pooling - Reduce connection overhead Implement retry logic - Handle transient faults (error 40613, 40197) Use redirect connection mode - Better performance after initial connection Close connections promptly - Don't hold connections unnecessarily Azure-Specific Limitations Not Supported SQL Agent (use Azure Functions, Logic Apps) BULK INSERT from files (use Blob Storage) Linked servers (use Elastic Query) FILESTREAM Cross-database queries in same server (use Elastic Query) Workarounds Bulk Insert from Blob Storage -- Create credential CREATE DATABASE SCOPED CREDENTIAL BlobCredential WITH IDENTITY = 'SHARED ACCESS SIGNATURE', SECRET = 'your_sas_token';
-- Create external data source CREATE EXTERNAL DATA SOURCE BlobStorage WITH ( TYPE = BLOB_STORAGE, LOCATION = 'https://youraccount.blob.core.windows.net/container', CREDENTIAL = BlobCredential );
-- Bulk insert BULK INSERT MyTable FROM 'data.csv' WITH (DATA_SOURCE = 'BlobStorage', FORMAT = 'CSV', FIRSTROW = 2);
Elastic Query for Cross-Database -- On target database CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'password';
CREATE DATABASE SCOPED CREDENTIAL ElasticCredential WITH IDENTITY = 'username', SECRET = 'password';
CREATE EXTERNAL DATA SOURCE RemoteDB WITH ( TYPE = RDBMS, LOCATION = 'remote-server.database.windows.net', DATABASE_NAME = 'RemoteDatabase', CREDENTIAL = ElasticCredential );
CREATE EXTERNAL TABLE dbo.RemoteTable (...) WITH (DATA_SOURCE = RemoteDB);
Cost Optimization Reserved Capacity Up to 72% savings vs pay-as-you-go 1-year or 3-year terms Exchange/refund flexibility Right-Sizing -- Check if over-provisioned SELECT AVG(avg_cpu_percent) AS avg_cpu, MAX(avg_cpu_percent) AS max_cpu, AVG(avg_data_io_percent) AS avg_io, MAX(avg_data_io_percent) AS max_io FROM sys.dm_db_resource_stats WHERE end_time >= DATEADD(day, -7, GETUTCDATE());
-- If avg < 40% consistently, consider downsizing
Hyperscale Cost Considerations Compute: Per-second billing Storage: Per-hour billing for used space Read replicas: Additional compute cost Memory not automatically released (monitor and scale appropriately)