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IO_COMPLETION

MEDIUM I/O

#io#sync#backup

Overview

Occurs when waiting for synchronous I/O operations to finish. Often related to network I/O, backup/restore, or bulk insert operations.

Key Metrics

Metric	Description
Wait Type	`IO_COMPLETION`
Category	Io
Severity	MEDIUM

Troubleshooting

1. Identify the source

Use the following query to identify the top queries contributing to IO_COMPLETION 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 = 'IO_COMPLETION'
ORDER BY wait_time_ms DESC;

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