What is deadlock priority and how to address in SQL Server

In SQL Server, deadlock priority is a mechanism that allows you to influence the selection of the transaction that will be chosen as the deadlock victim when a deadlock occurs. You can use deadlock priority to specify the importance of individual transactions in the event of a deadlock.

To address deadlock priority in SQL Server, you can consider the following:

1. Setting deadlock priority:
   • You can use the SET DEADLOCK_PRIORITY statement to specify the priority of a session or transaction.
   • The priority levels range from -10 to 10, where -10 is the lowest priority and 10 is the highest.
   • By setting the deadlock priority, you can influence the selection of the victim transaction when a deadlock occurs.

Here's an example of how to set the deadlock priority for a session:

SET DEADLOCK_PRIORITY LOW; -- Set the deadlock priority to low
  

2. Adjusting transaction logic:

   • Design your transaction logic to handle the potential impact of being chosen as the deadlock victim based on the assigned deadlock priority.
   • Consider implementing retry logic for transactions with lower deadlock priority after being chosen as the deadlock victim.

3. Analyzing and tuning deadlock priority:

   • Evaluate the impact of deadlock priority settings on your application's transactions and overall performance.
   • Tune the deadlock priority based on the specific requirements and characteristics of your application to effectively manage deadlocks.

It's important to carefully consider the implications of deadlock priority settings in SQL Server and design your transaction logic to handle deadlock situations appropriately. Understanding the behavior of deadlock priority in SQL Server is crucial for effectively addressing and managing deadlocks.