Description

Similar to HADR_SYNC_COMMIT, however this wait occurs while Secondary Replicas are attempting to catch-up with the Primary. This is typically seen after: adding a database to an Availability Group, setting the replication mode to synchronous, and when either replica comes online

Resolved by

DBAs and Developers

Suggested solutions

1. Ensure secondary replicas are adequately resourced. Specifically the transaction logs should be on fast storage
2. If possible do not leave Secondary Replicas offline longer than necessary. The Secondary Replica will take longer to become synchronised
3. Rewrite modification DML that performs small (row-by-row) changes. Batch modifications result in less transaction log usage and messages across the network
4. Remove unnecessary indexes, less messages and transaction log usage on modifications
5. Scale out database design

Additional research

Monitor SQL Server AlwaysOn Availability Groups
MSDN Blog: Monitor Performance for AlwaysOn Availability Groups

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