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Monitoring SQL Server database transaction log space

MSSQLTips author Greg Robidoux By:   |   Read Comments (6)   |   Related Tips: 1 | 2 | 3 | More > Monitoring

Problem
Keeping track of your transaction log usage is key to understanding how your database transaction logs are being used as well as keeping track of how much space the transaction logs are using.  Depending on the recovery model that is set within your database and also the backup jobs that you run, the size of your transaction log can vary quite a bit.  So what is the best way to keep track of the transaction log usage?

Solution
SQL Server has a command that you can run to see the current size of the transaction logs and how much space is currently being utilized. The command is DBCC SQLPERF(logspace).  This is a very simple command to run and interpret and this is key to getting an understanding of how your transaction logs are being used.

Here is sample output after running the command.

As you can see there are only four columns. Below is a description of each of these.

  • Database Name - Name of the database for the log statistics displayed.
  • Log Size (MB) - Actual amount of space available for the log.
  • Log Space Used (%) - Percentage of the log file currently occupied with transaction log information.
  • Status - Status of the log file. Always 0.

If you run this command at different times you will see the Log Space Used (%) increase and decrease depending on the activity in your database, the recovery model that you have set and also whether you are running transaction log backups.  Also, if your transaction logs are set to auto grow and/or auto shrink you will see the size of the file either increase or decrease again depending on activity.

To gain some further insight it would be helpful to capture this data at a set time and then go back and analyze the data at a later time.  This can be done by sending the output of this command to a table.

Below is a simple way of beginning this process.  There are three pieces of code here:

  1. Stored Procedure spSQLPerf - the only purpose of this command is to be able to send the output from the DBCC command into a temporary table
  2. Table logSpaceStats - this will store the long term stats data
  3. Stored Procedure spGetSQLPerfStats - this calls spSQLPerf and inserts the data into table logSpaceStats
CREATE PROC dbo.spSQLPerf
AS
DBCC 
SQLPERF(logspace)
GO
 


CREATE TABLE dbo.logSpaceStats
(
id INT IDENTITY (1,1),
logDate datetime DEFAULT GETDATE(),
databaseName sysname,
logSize decimal(18,5),
logUsed decimal(18,5)
)
GO
 


CREATE PROC dbo.spGetSQLPerfStats
AS
SET 
NOCOUNT ON

CREATE TABLE 
#tFileList
(
databaseName sysname,
logSize decimal(18,5),
logUsed decimal(18,5),
status INT
)

INSERT INTO #tFileList
       
EXEC spSQLPerf

INSERT INTO logSpaceStats (databaseNamelogSizelogUsed)
SELECT databasenamelogSizelogUsed
FROM #tFileList

DROP TABLE #tFileList
GO

After you have created the above components you need to call the procedure as follows to capture the information.  This can be done manually or you can setup a scheduled job to have this run every hour or some other set schedule.

sp_getSQLPerfStats

To take a look at the results just query the logSpaceStats table.  This can be done across the board or for an individual database.

SELECT FROM dbo.logSpaceStats

Next Steps

  • This is just one component of monitoring your server and your transaction log usage.
  • Review this data to see how space usage is being used as well as a guideline to size your transaction logs appropriately
  • After large transactions run these commands to see how much transaction log space is being used.


Last Update: 2/13/2007


About the author
MSSQLTips author Greg Robidoux
Greg Robidoux is the President of Edgewood Solutions and a co-founder of MSSQLTips.com.

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Comments and Feedback:
Tuesday, January 19, 2010 - 2:49:14 PM - olepadre Read The Tip

Is there a way to run the DBCC SQLPERF(logspace) on a remote server.  I have multiple Databases and I would like to run the collection stored procedure on remote servers and collect them all into one database on the monitoring server.


Monday, February 07, 2011 - 6:50:49 PM - James Read The Tip

My first instinct would be able to set up a linked server.    You should be able to pull the result back onto your monitoring server and store the results in a table


Tuesday, February 08, 2011 - 8:00:43 AM - Greg Robidoux Read The Tip

If you are using SQL Server 2008 you can use Central Management Servers.  Check out these tips:

http://www.mssqltips.com/tip.asp?tip=1767

This tip shows how you can do this without CMS.

http://www.mssqltips.com/tip.asp?tip=2086


Monday, April 09, 2012 - 1:31:55 AM - Vignesh K Read The Tip

Hello,

Log file sizes in our Database are, mdf = 61GB, log.ldf = 197MB and log1.ldf = 38MB.
But when I run the "DBCC SQLPERF(LOGSPACE)" command the Log size shown is 229MB and Log% as 4.5%.
Is this Log size value equal to sum of the 2 ldf files?
The other We tried to kill a long running process. At that time the Log% was shown as 99% for a long time.
This caused the mdf file size to shoot upto 90GB. Is this possible? (i.e.) Increase in the size of ldf file cause an increase in mdf file size too?

Your help is much appreciated

Thanks in advance


Thursday, January 10, 2013 - 10:13:20 AM - Luis Herrera Read The Tip

Very well this solution.. thanks


Tuesday, May 07, 2013 - 5:33:40 AM - Miklovic Marcel Read The Tip

Alternative solution:

 SELECT *

FROM sys.dm_os_performance_counters 

WHERE counter_name='Percent Log Used'



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