Azure SQL Database Troubleshooting

Comprehensive guide to diagnosing and resolving common issues with Azure SQL Database.

Common Problem Areas

This section covers the most frequently encountered issues when working with Azure SQL Database, along with strategies to identify their root causes.

  • Connectivity Issues: Problems establishing connections to your Azure SQL Database instance.
  • Performance Bottlenecks: Slow query execution, high CPU utilization, or insufficient throughput.
  • Error Messages: Understanding and interpreting specific error codes and messages.
  • Resource Limits: Exceeding DTU or vCore limits, storage capacity.
  • Throttling: Understanding and mitigating request throttling.

Connectivity Troubleshooting

When you can't connect to your Azure SQL Database, consider the following steps:

  • Firewall Rules: Ensure that your client IP address is allowed through the Azure SQL Server firewall. Check the "Firewall and virtual networks" settings in the Azure portal.
  • Virtual Network Service Endpoints: If using VNet integration, verify that the service endpoints are correctly configured and that your resources are within the allowed subnets.
  • Private Endpoints: For enhanced security, if you're using Private Endpoints, confirm that DNS resolution is working correctly and that the private IP address is accessible from your client.
  • Authentication: Double-check your connection string for correct username, password, and authentication method (SQL Authentication vs. Azure AD Authentication).
  • Network Latency: High latency between your client and the Azure region can impact connection stability.
Tip: Use the ping and tracert (or traceroute) commands to diagnose network path issues.

Performance Issues

Diagnosing and resolving performance problems requires a systematic approach:

  • Query Performance:
    • Identify long-running or resource-intensive queries using Query Performance Insight or dynamic management views (DMVs) like sys.dm_exec_query_stats.
    • Analyze query execution plans to understand where bottlenecks occur (e.g., missing indexes, inefficient joins).
    • Optimize T-SQL code and consider using parameterized queries.
  • Resource Utilization:
    • Monitor DTU or vCore usage, CPU, memory, and I/O percentages in the Azure portal or using DMVs.
    • If resources are consistently maxed out, consider scaling up your database tier or compute size.
  • Indexing: Ensure appropriate indexes are in place for frequently queried columns. Use the Database Advisor in the Azure portal for index recommendations.
  • Blocking: Identify and resolve blocking sessions that are preventing other queries from executing. Use sp_who2 or DMVs like sys.dm_exec_requests and sys.dm_os_waiting_tasks.
SELECT TOP 10 qs.total_elapsed_time / qs.execution_count AS avg_elapsed_time, qs.total_logical_reads / qs.execution_count AS avg_logical_reads, SUBSTRING(st.text, (qs.statement_start_offset/2)+1, ((qs.statement_end_offset - qs.statement_start_offset)/2)+1) AS statement_text, qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) st CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp ORDER BY avg_elapsed_time DESC;

Error Handling and Diagnostics

When encountering specific errors, consult the Azure SQL Database documentation for detailed explanations and resolutions.

  • Error Codes: Many SQL Server error codes apply to Azure SQL Database. A quick search for the specific error number (e.g., "SQL Error 1205") can often lead to relevant solutions.
  • Azure Monitor and Logs: Configure diagnostic settings to send logs and metrics to Azure Monitor. This provides valuable insights into database activity and potential issues.
  • SQL Server Error Log (Managed): While you don't have direct access to the physical error log, Azure SQL Database generates similar information that can be queried via DMVs or captured through diagnostic logs.
  • Connection Errors: Look for error messages like "Login failed for user...", "Cannot open server...", or "A network-related or instance-specific error occurred...".

Further Resources