SQL Server Binary Log Reader FAQs

Find answers to frequently asked questions about the Binary Log Reader incremental sync method for the SQL Server connector.

Why does Binary Log Reader require CDC to be enabled, even when using the backup transaction log method?

Binary Log Reader requires CDC because enabling CDC activates the supplemental logging that Binary Log Reader needs to reconstruct complete row changes from the transaction log. Binary Log Reader does not read CDC capture tables. For more information, see Supplemental logging.

Will CDC cause significant additional computations in my database?

Typically, no. After you enable CDC for Binary Log Reader, the log truncation mode determines whether the CDC capture job is retained or dropped. In Fivetran and User-managed modes, the CDC capture job is dropped. In SQL Server Agent mode, it is retained. For more information, see Configuring log truncation with Binary Log Reader.

What advances the replication truncation point?

The log truncation mode determines what advances the replication truncation point. In Fivetran mode, Fivetran advances it. In User-managed mode, you are responsible for advancing it. In SQL Server Agent mode, SQL Server's native CDC capture job advances it. For more information, see Configuring log truncation with Binary Log Reader.

Does Fivetran use sp_repldone?

Yes. In Fivetran log truncation mode, Fivetran uses the sp_repldone stored procedure to advance the replication truncation point. In User-managed mode, Fivetran does not use sp_repldone; you are responsible for running it to advance the replication truncation point. For more information, see Configuring log truncation with Binary Log Reader.

What happens to the transaction log when the connection is paused or a sync fails?

The log truncation mode determines whether the transaction log continues to truncate when a sync is paused or fails. In Fivetran mode, paused or failed syncs can lead to transaction log growth because Fivetran stops advancing the truncation point. In User-managed and SQL Server Agent modes, a paused or failed Fivetran sync does not affect how the truncation point is advanced. In User-managed mode, transaction log growth depends on how often you run the sp_repldone to advance the truncation point. In SQL Server Agent mode, transaction log growth depends on whether SQL Server Agent and the CDC capture job continue running and advancing the truncation point. For more information, see Configuring log truncation with Binary Log Reader.