LCK_M_IU

Overview

Occurs when waiting for an intent update (IU) lock. Common during index operations where the intent update at the table level is blocked by concurrent shared locks.

Key Metrics

Metric	Description
Wait Type	LCK_M_IU
Category	Blocking
Severity	MEDIUM

Troubleshooting

1. Identify the source

Use the following query to identify the top queries contributing to LCK_M_IU 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 = 'LCK_M_IU'
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_requests for blocking analysis

See Also

• sys.dm_os_wait_stats (Transact-SQL)
• sys.dm_exec_session_wait_stats (Transact-SQL)
• sys.dm_os_waiting_tasks (Transact-SQL)