Why is my Database Throwing a 'Timeout Expired' Error During Application Startup?

Database timeout error: "The timeout has expired. The timeout expired before the operation was completed, or the server was unresponsive"

Experiencing the troublesome “timeout expired” error on a high-traffic website can be confusing and frustrating. In order to understand the reasons and effectively solve this problem, let’s dive into the details.

Error reason:

This error usually occurs when the execution time of a database query or command exceeds the configured timeout. The timeout is specified by the Command Timeout setting in the connection string. When this time threshold is exceeded, SQL Server terminates the operation.

Possible causes and solutions:

• Deadlock: A deadlock occurs when two or more transactions are waiting for each other to release resources. This situation can be detected using SQL Server Activity Monitor. To resolve this issue, modify your code or database structure to avoid deadlocks.
• Outdated database statistics: Incorrect statistics can cause SQL Server to estimate that a query is executing faster than it actually is. To resolve this issue, run the "sp_updatestats" and "dbcc freeproccache" commands to update statistics and optimize query plans.
• Complex queries: Overly complex queries can overwhelm the database server and cause timeouts. Consider simplifying the query or investigating alternative query optimization techniques.
• Long-running transactions: An extended transaction may prevent other operations from accessing the database. Identify and optimize code or database processes to minimize transaction times.
• Server Load: Excessive server load can cause timeout errors. Scale server infrastructure or optimize code to reduce resource consumption during peak traffic periods.

Additional troubleshooting steps for Application_Start:

In your specific case, the timeout occurs during the Application_Start method. The code snippet shows that you are resetting the "OnlineUsers" table by calling the stored procedure Update_SessionEnd_And_Online. Due to the large number of records in the table, the update operation may take a lot of time.

• Consider optimizing stored procedures to improve performance.
• Alternatively, consider performing the update operation during off-peak hours, or use a SQL job to handle this task.
• Check the Application_Start method for any other long-running operations that might cause a timeout.

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