RESOURCE_SEMAPHORE
CRITICAL Triage
#memory#grant#query-memory#pressure
Related diagnostic scripts:
Overview
Occurs when a query cannot start execution because it is waiting for memory grant. High values indicate the server is out of query memory — queries are queued until memory is available. A memory pressure crisis.
Key Metrics
| Metric | Description |
|---|---|
| Wait Type | RESOURCE_SEMAPHORE |
| Category | Triage |
| Severity | CRITICAL |
Troubleshooting
1. Identify the source
Use the following query to identify the top queries contributing to RESOURCE_SEMAPHORE 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 = 'RESOURCE_SEMAPHORE'
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