Waitopedia is a comprehensive resource of information about SQL Server waits.

The description shown below is the top answer as voted by the Spotlight community.

The charts are based on 2.1 TB of data collected from 4207 instances uploaded by 323 Spotlight users over an 8 week period.


Category: IO
SQL Server versions: 2000, 2005, 2008, 2008 R2, 2012, 2014, 2016, 2017


2 Answers


Occurs when a task is waiting for I/Os to finish. Information from Microsoft®


Used to indicate a worker is waiting on a asynchronous I/O operation to complete not associated with database pages

Somewhat common

This wait is somewhat common for most instances

For each of 4207 instances, we ranked ASYNC_IO_COMPLETION on how frequent it is compared to all other recent waits. The chart shows the total of all rankings.

Prevalence of ASYNC_IO_COMPLETION across the Spotlight Population

For 64 % of hours with this wait, average wait time is less than 570 ms

For each instance, we found all the recent hours when it had a ASYNC_IO_COMPLETION wait. We found the average latency for each of those hours.

2903 instances contributed data to this chart

Latency Distribution of ASYNC_IO_COMPLETION across the Spotlight Population