HADR_SYNC_COMMIT wait when running Async with very large Log Send Que

• Bill

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  November 4, 2021 at 3:58 pm

  #3947947

  Hello all,

  Edit:  Posted here because I last saw this issue on a SQL 2016 server.

  We use AOAG extensively for our production DBs across 2014, 2016, and 2019 SQL Instances.  All our AOAG setups use Async commit without exception.

  We occasionally see an issue where the Log Send Rate drops very low (500KB\sec) causing the Log Send Que to rise quite a bit.  The Log Send Que will get as high as 100,000,000KB+.  I noticed on the Primary server that all the wait time was taken up by HADR_SYNC_COMMIT.

  In my research for HADR_SYNC_COMMIT I'm seeing that this wait stat only applies to Synchronous mode.  Since we're in Async we should never see this wait (as far as I've found).

  Does anyone have any idea why this wait will occur with very large Log Send Ques?  Or maybe a better question is, what situation in Async mode will cause this wait to occur?

  Thank you in advance for any help!

  -Bill

  • This topic was modified 3 years ago by  Bill.

• Site Owners

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  November 5, 2021 at 4:10 pm

  #3948406

  Thanks for posting your issue and hopefully someone will answer soon.

  This is an automated bump to increase visibility of your question.