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: Other
SQL Server versions: 2012, 2014, 2016, 2017


1 Answer


A SQL Server thread is waiting to switch from non-preemptive mode (scheduled by SQL Server) to preemptive mode (scheduled by the operating system) in order to invoke Windows Server Failover Clustering APIs. Information from Microsoft®

Very rare

This wait never occurs for most instances

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

Prevalence of HADR_CLUSAPI_CALL across the Spotlight Population

For 28 % of hours with this wait, average wait time is around 250 ms

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

629 instances contributed data to this chart

Latency Distribution of HADR_CLUSAPI_CALL across the Spotlight Population