Why select query is waiting on HADR_SYNC_COMMIT?

by Alex Bochkov   Last Updated August 13, 2018 20:06 PM

We have two AlwaysOn nodes in sync commit. Occasionally select queries are waiting on HADR_SYNC_COMMIT. What is the underlying process that causes it?

  • SQL Server 2016 SP1 CU5.
  • client sessions are using READ COMMITTED isolation level
  • Allow Snapshot Isolation and Is Read Committed Snapshot On are set to True. But snapshot isolation is not being used because client is enforcing READ COMMITTED.

Query example from primary replica: select * from dbo.photoFileMetaData where [email protected] Wait info: (780ms)HADR_SYNC_COMMIT Status: suspended

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