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


Waiting when the number of outstanding unacknowledged AlwaysOn messages is over the out flow control threshold. This is on an availability replica-to-replica basis (not on a database-to-database basis). Information from Microsoft®

Very rare

This wait never occurs for most instances

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

Prevalence of HADR_TRANSPORT_FLOW_CONTROL across the Spotlight Population

For 95 % of hours with this wait, average wait time is around 980 ms

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

1 instance contributed data to this chart

Latency Distribution of HADR_TRANSPORT_FLOW_CONTROL across the Spotlight Population