The SQL Server Deadlocks page helps identify deadlock events and the queries or sessions involved. Use it to understand concurrency conflicts and recurring blocking patterns.
What To Review
- Deadlock time.
- Involved sessions, databases, and objects.
- Victim and survivor process details.
- Query text where available.
- Deadlock graph or structured detail where available.
Workflow
- Open Deadlocks for the SQL Server.
- Sort by time to find recent events.
- Review involved objects and queries.
- Compare with Activity and Waits.
- Use Cached SQL or Query Store to inspect recurring statements.
Live And Historical Deadlock Data
The SQL Server Deadlocks page includes the Mini DBA Time Range selector. Use Live for the current deadlock view, or switch to Last Hour, Last 12 Hours, Last Day, Last Week, or Custom to review historical deadlock events. Mini DBA loads and caches the selected historical deadlock dataset for the current console session and server context, so reviewing event details and moving between related evidence stays quick after the range has loaded. Use Back to Live to resume live updates, then choose another historical range when you need a different incident window.
How To Investigate Recurring Deadlocks
For recurring deadlocks, look for the pattern rather than treating each event as isolated. Identify the tables, indexes, stored procedures, isolation levels, and application paths involved. Deadlocks often improve when transactions are shorter, objects are accessed in a consistent order, useful indexes reduce scan time, or retry logic is added at the application layer.
Use deadlock evidence with query history. A victim query may not be the root cause if another session held locks too long. Compare deadlock participants with Activity, Query Store, and Indexes.
SQL Server Deadlocks FAQ
Is a deadlock always a database bug?
No. Deadlocks can happen in busy systems. Recurring deadlocks that affect users usually deserve investigation.
Why do I need Extended Events permissions?
Extended Events can capture deadlock information quickly and reliably. Without the related permission, Mini DBA may have less deadlock detail.
What is the first thing to fix?
Start by finding the repeated object and query pattern. Then reduce lock duration, improve indexing, or adjust transaction order where appropriate.
Next Steps After A Deadlock
After a deadlock is identified, capture the victim query, competing query, database, objects, indexes, time, and application workflow. Then review whether transactions access tables in a consistent order and whether indexes allow SQL Server to lock fewer rows. Repeating deadlocks should be treated as an application or schema tuning task, not just an alert to acknowledge.