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

This is an idle wait and so it can be safely ignored.


2 Answers


When the redo thread is blocked, an extended event called sqlserver.lock_redo_blocked is generated. Additionally, you can query the DMV sys.dm_exec_request on the secondary replica to find out which session is blocking the REDO thread, and then you can take corrective action. The following query returns the session ID of the read-only query that is blocking the redo thread.

select session_id, command, blocking_session_id, wait_time, wait_type, wait_resource from sys.dm_exec_requests where command = 'DB STARTUP'

Source: https://technet.microsoft.com/en-us/library/dn135336(v=sql.110).aspx


The view is named sys.dm_exec_requests

Very rare

This wait never occurs for most instances

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

Prevalence of REDO_THREAD_PENDING_WORK across the Spotlight Population

For 43 % of hours with this wait, average wait time is around 100 ms

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

363 instances contributed data to this chart

Latency Distribution of REDO_THREAD_PENDING_WORK across the Spotlight Population