Andrew Calvett's SQL Server Blog

I read Tony Rogerson’s blog on Virtual Log Files today and it reminded me that i really should knock up a little report to list all databases on a server and the number of VLF’s per database. Since I had been busy writing some other Operational reports I was in the right frame of mind so knocked up what you see below.

The Report code

CREATE TABLE #VLFS (fileid INT,filesize bigint,startoffset bigint,fseqno bigint,status INT,parity INT,createlsn VARCHAR(1000))

CREATE TABLE #Results (SRV_Name NVARCHAR(500),Database_Name NVARCHAR(500),VLFS INT)

EXEC MASTER.dbo.sp_msforeachdb

    @command1 = 'USE ? INSERT INTO #VLFS EXEC(''DBCC LOGINFO WITH TABLERESULTS'')',

    @command2 = 'insert into #Results SELECT @@SERVERNAME,''?'',count(*) from #vlfs',

    @command3 = 'truncate table #vlfs'

--For this example i`ve just returned the results but you can

--just as easily write the results to a local or central server.

--I write mine to a central server for reporting on.

SELECT * FROM #Results

DROP TABLE #vlfs

DROP TABLE #Results

Example output

For me the beauty of this little report is that i have set it up so that it runs on all 150 of my servers distributed around the world and logs to my central logging server. From here I get one report that tells me the databases and the servers they are hosted on that have excessive VLF’s. Having said that in a well managed environment i should never find any databases with lots of VLF’s……..

You may also be wondering "How many VLF’s are too many?". Tony did not cover this but Kimberly Tripp did in a post she put up a few years ago (See point 8) which was when I first learned about VLF’s. I don’t however think this is a hard and fast number and obviously the performance gains will be less if your not far off this number.

The last thing I am going to mention in this post is part of the code I used in the report. I used the undocumented procedure sp_msforeachdb. This is a great little procedure that will cycle through your databases executing up to 3 commands. To use it, where you would have put a database name you put a ‘?’ and its as simple as that! Incidentally there is also a sp_msforeachtable.