WRITELOG
HIGH I/O
#io#log#transaction#flush
Related diagnostic scripts:
Overview
Occurs when waiting for the transaction log to be flushed to disk. One of the most important I/O signals. High WRITELOG indicates log drive latency, excessive transactions, or insufficient log throughput.
Key Metrics
| Metric | Description |
|---|---|
| Wait Type | WRITELOG |
| Category | Io |
| Severity | HIGH |
Troubleshooting
1. Identify the source
Use the following query to identify the top queries contributing to WRITELOG waits:
SELECT TOP 10
[Wait Type] = wait_type,
[Wait Seconds] = wait_time_ms / 1000,
[Wait Count] = waiting_tasks_count,
[Avg Wait Ms] = wait_time_ms / NULLIF(waiting_tasks_count, 0)
FROM sys.dm_os_wait_stats
WHERE wait_type = 'WRITELOG'
ORDER BY wait_time_ms DESC;2. Related diagnostics
- Review overall wait statistics using
sys.dm_os_wait_stats - Check session-level waits via
sys.dm_exec_session_wait_stats - Correlate with
sys.dm_exec_requestsfor blocking analysis