Background

Error 10929 occurs when an Azure SQL Database session is terminated due to resource throttling. This means that the database has reached its resource usage limit, such as CPU, memory, or IOPS (Input/Output Operations Per Second), and the system terminates the session to maintain overall performance. This typically happens in lower service tiers or during heavy workloads.

Summary Table

Error Explanation

Azure SQL Database dynamically manages resource allocations across all databases within the same server. When resource usage exceeds the allowed threshold for a given service tier (e.g., Standard, Premium), the system will throttle resources to prevent overuse. If a session’s resource consumption exceeds the limit, Azure SQL may terminate the session, resulting in error 10929.

The error message is typically:

Error 10929: Resource ID: %d. The %s minimum guarantee is %d, maximum limit is %d and the current usage for the database is %d. However, the server is currently too busy to support requests greater than the minimum guarantee. See 'http://go.microsoft.com/fwlink/?LinkId=267637' for assistance.

Common Causes

1. Excessive Resource Usage: The database is consuming more resources than allocated by the service tier, such as CPU, memory, or IOPS.
2. Heavy Workloads: High traffic or large queries are exceeding resource thresholds.
3. Inadequate Service Tier: The selected service tier has lower resource limits and is unable to handle the workload.
4. Concurrent Queries: Too many concurrent sessions or long-running queries causing resource contention.

Steps to Troubleshoot and Resolve Error Code 10929

1. Identify Resource Bottleneck

To resolve error 10929, the first step is to identify which resource (CPU, memory, I/O) is being throttled. You can do this by monitoring the database’s resource usage in the Azure Portal.

Steps to Monitor Resource Usage:

1. Go to the Azure Portal.
2. Navigate to your SQL Database.
3. Under Monitoring, select Metrics.
4. Monitor key metrics such as DTU usage (for DTU-based databases) or vCore usage (for vCore-based databases).

Check if any of the metrics (CPU, memory, or I/O) are consistently near 100%, which would indicate that the database is hitting resource limits.

Example:

You are running a Standard S2 database with a maximum of 50 DTUs. When monitoring resource usage, you see that DTU usage consistently spikes to 100%, indicating the database is maxing out its available resources.

2. Identify and Optimize Heavy Queries

If your database is under resource pressure due to heavy queries or long-running transactions, optimizing these queries can significantly reduce resource consumption.

Steps to Identify Heavy Queries:

1. Go to Query Performance Insight in the Azure Portal.
2. Identify the top queries consuming the most resources (CPU, memory, or I/O).
3. Use the Query Store to track the performance of these queries.

Example Query:

SELECT TOP 10
    qs.total_worker_time AS CPU_Time,
    qs.execution_count,
    qs.total_physical_reads AS Reads,
    qs.total_logical_writes AS Writes,
    q.text AS QueryText
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) q
ORDER BY qs.total_worker_time DESC;

This query retrieves the most resource-intensive queries based on CPU time. Once identified, you can optimize them by adding appropriate indexes or breaking them into smaller, more manageable queries.

3. Upgrade Service Tier for More Resources

If the current workload consistently exceeds the available resources, consider upgrading to a higher service tier that offers more CPU, memory, and IOPS.

Steps to Upgrade the Service Tier:

1. Go to the Azure Portal.
2. Navigate to your SQL Database instance.
3. Under Settings, click on Pricing tier.
4. Select a higher service tier that fits your workload (e.g., upgrading from Standard S2 to Standard S3 or Premium P1).
5. Click Apply.

Example:

If you’re using the Standard S2 tier with 50 DTUs and frequently hitting resource limits, you can upgrade to Standard S3 with 100 DTUs or Premium P1 for better performance.

4. Reduce Concurrent Connections and Transactions

Too many concurrent connections or transactions can overwhelm the database and lead to resource throttling. Reducing the number of concurrent sessions or optimizing transactions can help manage resource usage.

Steps to Limit Concurrent Connections:

1. Monitor the number of active connections using the following query:

SELECT COUNT(*) AS ActiveConnections
FROM sys.dm_exec_sessions
WHERE status = 'running';

1. Limit the number of concurrent connections in your application by pooling connections or handling queries in batches.

5. Implement Query Throttling and Retrying

If you can’t immediately upgrade the service tier, consider implementing query throttling in your application. This involves queuing or delaying queries when the database is under heavy load and retrying failed operations after a brief delay.

Example Retry Logic in C#:

public void ExecuteWithRetry()
{
    int retryCount = 3;
    int delay = 2000; // 2 seconds
    for (int i = 0; i < retryCount; i++)
    {
        try
        {
            using (SqlConnection conn = new SqlConnection("Your Connection String"))
            {
                conn.Open();
                // Execute your SQL query here
                break; // Exit loop if the query is successful
            }
        }
        catch (SqlException ex) when (ex.Number == 10929)
        {
            // Log error and wait before retrying
            System.Threading.Thread.Sleep(delay);
        }
    }
}

This code retries the query up to 3 times, waiting 2 seconds between each attempt. This can help in situations where transient resource limitations cause error 10929.

6. Scale Out with Read Replicas

If your workload is mostly read-heavy, consider scaling out your application by using read replicas. This distributes the read load across multiple databases, reducing the pressure on the primary database.

Steps to Add a Read Replica:

1. Go to the Azure Portal.
2. Navigate to your SQL Database.
3. Under Settings, select Geo-Replication.
4. Add a read-only replica in another region to distribute the load.

7. Monitor and Set Alerts

To prevent future occurrences of error 10929, set up monitoring and alerts in Azure to notify you when resource usage approaches the limit.

Steps to Set Alerts:

1. Go to Azure Monitor in the Azure Portal.
2. Create an alert rule for DTU usage (for DTU-based models) or CPU/IO usage (for vCore-based models).
3. Configure the alert to notify you when resource usage exceeds a certain threshold (e.g., 80%).

Workarounds

• Optimize Queries: Identify and optimize resource-intensive queries.
• Throttling & Retry Logic: Implement throttling and retry logic in the application to handle transient resource throttling.
• Scale-Out: Use read replicas to distribute the load.

Solutions

1. Upgrade Service Tier: Upgrade to a higher tier (e.g., from Standard S2 to Premium P1) to increase available resources.
2. Reduce Concurrent Connections: Limit the number of concurrent connections or transactions to reduce resource contention.
3. Optimize Queries: Identify resource-heavy queries and optimize them using indexing, partitioning, or query rewriting.
4. Implement Query Retry Logic: Add retry logic to handle resource throttling and transient errors.

Example Scenario

Let’s say you have an e-commerce application running on an Azure SQL Database Standard S2 instance. During peak hours, users encounter Error 10929, and transactions are failing. After investigating, you find that CPU and DTU usage are constantly hitting 100%, indicating resource limitations.

Step 1: Check resource metrics in the Azure Portal. You notice that DTU usage frequently spikes to 100%.

Step 2: Identify heavy queries using the following query:

SELECT TOP 10
    qs.total_worker_time AS CPU_Time,
    qs.execution_count,
    q.text AS QueryText
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) q
ORDER BY qs.total_worker_time DESC;

Step 3: Optimize the top resource-consuming queries by adding indexes.

Step 4: If optimization is not enough, upgrade to the Premium P1 tier to get more CPU, memory, and IOPS.

Step 5: Implement query retry logic in the application to handle any transient resource throttling.