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Full backup not emptying transaction log Expand / Collapse
Posted Thursday, November 8, 2012 6:39 AM


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I have a database that process a lot of transaction late at night. It is set to full recovery mode. Every night I do a full backup of the database, but the log file does not empty out. It just continues to grow and never seems to release old transactions after a backup. As a quick fix, which i don't like, I will temporarily switch recovery mode to simple->truncate log file->set recovery mode to full->then full backup of database. Any ideas why the transaction log does not empty out after a full backup and continues to grow?

Post #1382464
Posted Thursday, November 8, 2012 6:47 AM



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A full backup doesn't backup the transaction log, you need to take regular transaction log backups to make the log re-usable and stop it from growing out of control.

Managing Transaction Logs -

Stairway to Transaction Log Management -

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Post #1382467
Posted Thursday, November 8, 2012 7:03 AM
SSChasing Mays

SSChasing MaysSSChasing MaysSSChasing MaysSSChasing MaysSSChasing MaysSSChasing MaysSSChasing MaysSSChasing Mays

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I recommend you read Paul Randal's blog about backup myths:

30-05) a full or differential backup clears the log

No. A log backup includes all the log since the last log backup - nothing can change that - no matter whether that log was also backed up by a full or differential backup. I had a famous argument on Twitter last year and wrote this blog post as proof: Misconceptions around the log and log backups: how to convince yourself. In the FULL or BULK_LOGGED recovery models, the *only* thing that clears the log is a log backup.

Post #1382472
Posted Thursday, November 8, 2012 9:11 AM



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If you're not taking log backups for point-in-time restore capability, why is the DB in full recovery model in the first place?

Gail Shaw
Microsoft Certified Master: SQL Server, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

Post #1382561
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