SQL Server 2008 Change Data Capture

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One of the things that isn’t really clear form all the blurb about SQL Server 2008 is how the various new features affect each other and what’s already in SQL Server. So I wasn’t surprised to see questions being asked about Change Data Capture (CDC) and its affect on the log and specifically log shipping.

CDC is in some ways similar to transactional replication, they both rely on the transaction log to work out what’s been happening to the database as they both use the same server entry points (sp_replcmds and sp_repldone) to advance the truncation point in the log.

In this cases the truncation point is no longer the last committed transaction, but the last committed transaction that hasn’t been harvested by these features as these are in the active portion of the log.

Back to my original question does this mean you can’t use log shipping and CDC? Yes you can and this feature is improved upon in SQL Server 2008 as the log shipping traffic is now compressed.

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