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sql-serverbackuptransaction-logdbcc

DBCC SHRINKFILE on log file not reducing size even after BACKUP LOG TO DISK

I've got a database, [My DB], that has the following info:
SQL Server 2008
MDF size: 30 GB
LDF size: 67 GB

I wanted to shrink the log file as much as possible and so I started my quest to figure out how to do this. Caveat: I am not a DBA (or even approaching a DBA) and have been progressing by feel through this quest.

First, I just went into SSMS, DB properties, Files, and edited the Initial Size (MB) value to 10. That reduced the log file to 62 GB (not exactly the 10 MB that I entered). So, I attached SQL Profiler, saw that DBCC SHRINKFILE was being called. I then entered that command into the query editor and here's the results.

DBCC SHRINKFILE (N'My DB_Log' , 10)

And the output was:

Cannot shrink log file 2 (My DB_Log) because the logical log file located at the end of the file is in use.
DbId   FileId      CurrentSize MinimumSize UsedPages   EstimatedPages
------ ----------- ----------- ----------- ----------- --------------
8      2           8044104     12800       8044104     12800

(1 row(s) affected)

DBCC execution completed. If DBCC printed error messages, contact your system administrator.

I then did some research on that and found this:

http://support.microsoft.com/kb/907511

Which says that I need to backup the log file before the shrinkfile so that the virtual log files will be released and the shrinkfile can do its job - I don't know what that means... I'm just paraphrasing here :)

So, I figured I'd try to backup the log file and then do a DBCC SHRINKFILE (and I changed the new log file size to 12800 since that was the MinimumSize identified in the output of the previous DBCC SHRINKFILE command)

BACKUP LOG [My DB] TO DISK = 'D:\SQLBackup\20110824-MyDB-Log.bak'
GO
DBCC SHRINKFILE (N'My DB_Log' , 12800)
GO

The result was the same as the first go around. I can only get the log file down to 62 GB.

I'm not sure what I'm doing wrong and what I should try next.

Solution

  • In addition to the steps you have already taken, you will need to set the recovery mode to simple before you can shrink the log.

    THIS IS NOT A RECOMMENDED PRACTICE for production systems... You will lose your ability to recover to a point in time from previous backups/log files.

    See example B on this DBCC SHRINKFILE (Transact-SQL) msdn page for an example, and explanation.