Deadlock History for Database

Deadlock History for Database Report in Database Health Monitor

The Deadlock History report in Database Health Monitor provides a detailed log of past deadlocks within a specific database. This report helps DBAs analyze recurring deadlocks, identify patterns, and take corrective action to improve SQL Server performance.

Key Components of the Deadlock History Report

  1. Detailed Deadlock Events Log
    • Each row in the report represents a recorded deadlock event.
    • The data includes:
      • Deadlock ID – A unique identifier for each deadlock.
      • Date and Time – When the deadlock occurred.
      • Object Name – The table or index involved in the deadlock.
      • Index Name – The specific index that was locked.
      • Victim Query – The SQL statement that was chosen as the deadlock victim.
      • Blocking Query – The SQL statement that held the lock and caused the deadlock.
  2. Sorting and Filtering
    • The report allows users to sort and filter results by time, object, or query pattern to focus on critical deadlock incidents.
  3. Recurring Deadlocks Detection
    • By looking at time patterns, DBAs can determine whether deadlocks occur at specific times (e.g., during scheduled jobs or peak workloads).
    • In this screenshot, deadlocks are clustered around 4:00 PM on February 16, 2025, indicating a specific process or workload may be causing contention.
  4. Common Objects Involved
    • The report shows that most deadlocks involve dbo.TableA and dbo.TableB, meaning these tables are frequently accessed in ways that cause contention.
  5. Blocked Queries Analysis
    • By examining the victim and blocking queries, DBAs can identify query patterns that contribute to deadlocks.

How to Use the Deadlock History Report for Troubleshooting

  1. Identify Problematic Tables and Indexes
    • Look for objects appearing frequently in deadlock events.
    • If certain tables/indexes consistently cause deadlocks, they may need index tuning or query optimization.
  2. Analyze Query Patterns
    • Check the victim and blocking queries to identify patterns in the deadlocking behavior.
    • Determine if transactions access resources in conflicting order, leading to deadlocks.
  3. Optimize Transaction Ordering
    • Ensure all transactions access tables in a consistent order across all queries to prevent circular locking.
  4. Consider Isolation Level Changes
    • If deadlocks occur frequently, consider using Snapshot Isolation (RCSI) to reduce locking contention: ALTER DATABASE BigStuff SET READ_COMMITTED_SNAPSHOT ON;
  5. Reduce Long-Running Transactions
    • Check if transactions are open for too long, increasing the likelihood of deadlocks.
    • Keep transactions short and efficient.
  6. Indexing and Query Optimization
    • Ensure that tables involved in deadlocks have proper indexes to speed up query execution and reduce locking time.
    • Use covering indexes where applicable.

Conclusion

The Deadlock History Report in Database Health Monitor is a valuable tool for identifying and analyzing deadlock patterns over time. By reviewing the involved objects, queries, and timestamps, DBAs can take proactive steps to reduce deadlocks and improve SQL Server performance.