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SQL WRITE_COMPLETION Wait Type

Understanding WRITE_COMPLETION Wait Type in SQL Server

The WRITE_COMPLETION wait type in SQL Server occurs when SQL Server waits for a write operation to complete. This typically happens when SQL Server flushes data pages to disk, whether during checkpoints, lazy writer processes, or logging operations. These waits often indicate a bottleneck in the disk subsystem.

Performance Impact

Frequent WRITE_COMPLETION waits can lead to:

  • Slow Queries: Sluggish query performance due to delayed writes.
  • Longer Transactions: Prolonged transaction times, leading to potential locking issues.
  • Increased Latency: Higher latency in systems relying on fast writes, like OLTP workloads.

Tracking WRITE_COMPLETION with Database Health Monitor

Real-Time Monitoring

Use the Real-Time Waits Dashboard in Database Health Monitor to track WRITE_COMPLETION waits as they occur:

  1. Open Database Health Monitor.
  2. Access the Waits Dashboard.
  3. Look for WRITE_COMPLETION in the active waits list.

Historic Wait Monitoring

WRITE_COMPLETION Wait type

To identify trends, use Historic Wait Monitoring to review when and how often WRITE_COMPLETION waits occurred:

  1. Open Historic Wait Monitoring.
  2. Select a time range and filter by WRITE_COMPLETION.

This helps detect recurring issues and workload patterns that may contribute to WRITE_COMPLETION waits.

Resolving WRITE_COMPLETION Waits

To mitigate WRITE_COMPLETION waits, consider:

  • Improving Storage Performance: Upgrade to faster disks (e.g., SSDs) or balance I/O.
  • Managing Contention: Avoid overlapping high-I/O processes with peak database activity.
  • Tuning Checkpoints and Lazy Writes: Adjust checkpoint frequency and reduce memory pressure.

Conclusion

WRITE_COMPLETION waits, though often overlooked, can impact SQL Server Performance by signaling I/O issues. Monitoring these waits with Database Health Monitor helps you pinpoint problems and make informed decisions to optimize disk performance.

If you need expert help resolving WRITE_COMPLETION waits or other SQL Server Performance issues, explore our Managed Services at Stedman Solutions.


For more monitoring tools, visit Database Health Monitor.

 

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