SQL 2008 an Above: Shrinking the Transaction Log


We all know that, if a database is at the Full Recovery model but the transaction log is not being backed up, the transaction log size can grow exponentially.

I know that the remedy for this, in general, is to shrink the database while in Simple Recovery mode, switch to Full Recovery mode, and make sure that maintenance plans are backing up the transaction log at least every hour if possible.

But, prior to running the shrink statement, do you need to back up the transaction log?  Or, is this piece optional?

Below are scripts that I tend to run in this situation to backup the transaction log first and then shrink:

BACKUP LOG KLAI to disk = 'C:\SQLServerBackups\Logs\KLAI.BAK'

Again, is that first backup script necessary?


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Scott PletcherSenior DBACommented:
No, it's optional.  Typically you would not want to back it up once it's gotten that large, since it would take too long to re-apply it anyway, you'll never use that log backup.

Put the db into simple mode, do a db checkpoint, shrink the log, then take a full backup as a base for future log backups.

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Aneesh RetnakaranDatabase AdministratorCommented:
that depends on how valuable your data and the transaction logs are. If you sense the data is not at all worthy recovering from the log, then you can avoid it. In a true world I wouldn't shrink the log files as it increases the fragmentation.  Also the shrinkfile wont work until the virtual log files are released  that's why the backup log statement.  
here is an example how it should be done (again not recommended )

USE AdventureWorks2012;
-- Truncate the log by changing the database recovery model to SIMPLE.
ALTER DATABASE AdventureWorks2012
-- Shrink the truncated log file to 1 MB.
DBCC SHRINKFILE (AdventureWorks2012_Log, 1);
-- Reset the database recovery model.
ALTER DATABASE AdventureWorks2012
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Microsoft SQL Server

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