Azure Database Troubleshooting

Connectivity Issues

Problems connecting to your Azure database instance can stem from network configurations, firewall rules, or service availability.

Common Causes:

• Incorrect firewall rules blocking access.
• Virtual Network (VNet) or Private Endpoint misconfigurations.
• Service outages or maintenance.
• Authentication credential errors.

Solutions:

• Verify and update firewall rules in the Azure portal or via CLI/PowerShell.
• Check your VNet peering, subnet configurations, and NSG (Network Security Group) rules.
• Consult the Azure Service Health dashboard for ongoing incidents.
• Ensure you are using the correct connection strings and credentials.

Performance Degradation

Slow query execution, high CPU usage, or low throughput can significantly impact your application's performance.

Common Causes:

• Inefficient queries (missing indexes, table scans).
• Insufficient database tier or resource allocation.
• Locking and blocking issues.
• High I/O wait times.

Solutions:

• Analyze query performance using tools like Query Store or Performance Insights.
• Optimize SQL queries and add appropriate indexes.
• Monitor resource utilization (CPU, Memory, IOPS) and consider scaling up your database tier.
• Identify and resolve long-running transactions and deadlocks.

Example of checking database performance metrics:

-- Example Query for Azure SQL Database performance
SELECT
    SUM(total_elapsed_time / 1000.0 / COUNT(*)) AS avg_elapsed_time,
    SUM(logical_reads) / SUM(COUNT(*)) AS avg_logical_reads,
    SUBSTRING(qt.text, (su.statement_start_offset/2)+1,
        ((su.statement_end_offset - su.statement_start_offset)/2)+1) AS statement_text,
    COUNT(*) AS execution_count
FROM sys.dm_exec_query_stats AS qs
INNER JOIN sys.dm_exec_cached_plans AS cp ON qs.plan_handle = cp.plan_handle
CROSS APPLY sys.dm_exec_sql_text(plan_handle) AS qt
INNER JOIN sys.dm_exec_est(plan_handle) AS su ON qt.sql_handle = su.sql_handle
WHERE qt.text NOT LIKE '%sys.%' -- Exclude system queries
GROUP BY
    SUBSTRING(qt.text, (su.statement_start_offset/2)+1,
        ((su.statement_end_offset - su.statement_start_offset)/2)+1),
    qt.text
ORDER BY execution_count DESC;
                    

Replication Failures

Issues with replication between databases (e.g., Geo-replication, Always On Availability Groups) can lead to data inconsistencies.

Common Causes:

• Network latency or instability between replicas.
• Transaction log full on the primary.
• High transaction volume overwhelming the secondary.
• Configuration errors.

Solutions:

• Monitor replication lag and network conditions.
• Ensure sufficient space for transaction logs on all replicas.
• Distribute read workloads if possible to reduce pressure on the primary.
• Review the replication setup and partner configurations.

Security and Authentication

Problems with user access, role assignments, or authentication methods.

Common Causes:

• Incorrect username or password.
• Expired credentials.
• Insufficient permissions.
• Firewall blocking access from specific IPs.

Solutions:

• Verify credentials and ensure they are not expired.
• Check user roles and permissions within the database.
• Review Azure Active Directory integration and role assignments.
• Ensure the client IP is allowed through the database firewall.

Backup and Restore Problems

Failures during backup creation or restore operations.

Common Causes:

• Insufficient storage space for backups.
• Permissions issues for backup locations.
• Corrupted backup files (rare).
• Restore operations exceeding timeout limits.

Solutions:

• Monitor storage capacity for backup retention.
• Ensure appropriate access permissions are granted to the storage account.
• Contact Azure support if corruption is suspected.
• For large restores, consider using point-in-time restore with more resources or breaking down the restore.

Common Error Codes

Here's a list of frequently encountered error codes and their typical resolutions:

• Error 40613: Database is in a state that cannot be altered. - Often indicates the database is undergoing maintenance or is in a restricted state. Check Azure Service Health.
• Error 40540: The database [database_name] has reached its size quota. - Your database has run out of allocated storage. Scale up your database tier or clean up data.
• Error 49920: Cannot alter the server role... - You lack the necessary permissions to perform the requested server-level operation. Check your role assignments.
• Error 10060: Network-related or instance-specific error occurred while establishing a connection to SQL Server. - Firewall issues, incorrect server name, or the server is unreachable. Verify connection strings and firewall rules.