SQL Server 2019 Deadlock Detection and Resolution

A deadlock occurs when two or more queries hold locks that prevent each other from executing, leading to a stalled process. Detecting and resolving deadlocks efficiently is crucial for database performance and stability.

Step 1: Enable Deadlock Tracking with Extended Events

To track deadlocks in SQL Server 2019, set up an Extended Events session:

CREATE EVENT SESSION Deadlock_Detection ON SERVER 
ADD EVENT sqlserver.xml_deadlock_report 
ADD TARGET package0.event_file 
(SET filename='C:\ExtendedEvents\Deadlocks.xel'); 

ALTER EVENT SESSION Deadlock_Detection ON SERVER STATE=START;

This configuration captures deadlock reports for further analysis. For a more detailed guide on Extended Events, visit Microsoft Docs.

Step 2: Analyze and Resolve Deadlocks

Retrieve and analyze deadlock information using the following query:

SELECT 
    event_data.value('(event/data[@name="xml_report"]/value)', 'XML') AS DeadlockReport 
FROM sys.fn_xe_file_target_read_file('C:\ExtendedEvents\Deadlocks*.xel', NULL, NULL, NULL);

Deadlock Resolution Strategies:

1. Identify Conflicting Queries: Use the XML report to determine the involved transactions.
2. Reduce Locking Duration: Ensure transactions commit as soon as possible.
3. Use NOLOCK Hint Where Safe:SELECT * FROM Orders WITH (NOLOCK);
4. Optimize Indexing: Proper indexing reduces table scans and improves query performance.
5. Use TRY-CATCH Blocks: Handle deadlocks programmatically to retry failed transactions.

Identifying and Resolving Blocking in SQL Server 2019

Step 1: Check Blocking Queries

To identify blocking processes, run:

EXEC sp_who2;

Look for rows where BlkBy is not 0.

For a detailed view of blocking queries, use:

SELECT blocking_session_id AS BlockingSession, 
       wait_type, wait_time, blocking_session_id, 
       session_id AS BlockedSession, 
       status, command, wait_resource, 
       text AS BlockedQuery 
FROM sys.dm_exec_requests 
CROSS APPLY sys.dm_exec_sql_text(sql_handle) 
WHERE blocking_session_id <> 0;

Step 2: Fix Blocking Queries

• Identify and terminate blocking sessions (if necessary):
• KILL <SessionID>;
• Optimize indexes to improve query efficiency and reduce contention.
• Break long transactions into smaller, manageable units.
• Schedule resource-heavy queries during off-peak hours.

For more SQL Server performance optimization tips, check out our SQL Performance Guide.

By implementing these techniques, you can enhance SQL Server’s performance, minimize deadlocks, and ensure efficient transaction processing.

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