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.
SLEEP_MASTERDBREADY
Category: Idle
SQL Server versions: 2012, 2014, 2016, 2017
This is an idle wait and so it can be safely ignored.
What is SLEEP_MASTERDBREADY?
This wait has never occurred recently
SLEEP_MASTERDBREADY has not occurred recently on 4207 instances checked.