-> Check this article for more details on high Log Send Queue on Asynchronous Replica.

-> Log Send Queue shows the amount of log records in the log files of the primary database that has not yet been sent to the secondary replica. This value is sent to the secondary replica from the primary replica. Queue size does not include FILESTREAM files that are sent to a secondary.

-> I faced this issue recently on a Synchronous replica. We are aware of the reason why the log send queue increased, that was due to an Alter Index job as part of weekly maintenance. But we wanted to understand if we can do to speed up the process. It all depends on the network link and if we have reached the maximum limit, then there is not much we can do here other than waiting.

-> I tried below actions,

Restart Always on Endpoints on Secondary and then on Primary

ALTER ENDPOINT endpoint_name STATE = STOPPED
ALTER ENDPOINT endpoint_name STATE = STARTED

-> After above action, Log send queue gradually decreased and Always On database came to sync in sometime.

Thank You,
Vivek Janakiraman

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