Category Archives: SQL Server

Using DBCC UPDATEUSAGE to correct inaccuracies

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Recently a friend of mine asked to help, their SQL Server was not showing correct database free space information even when they have added new data file. As they add new data into their database the previously existing database data files are not getting filled with data, rather the newer data files are getting filled. 

As soon as I heard the issue from him, I knew it was the due to the inaccuracies in the catalog views maintained by the SQL Server. I suggested him to run DBCC UPDATEUSAGE command on his database to correct this inaccuracies. 

In order to show you an example, I simulated the same scenario on my personal server, I added few tables and filled plenty of data into those tables. Later I purged bulk of the data in those tables to simulate the inaccuracies. Below is an example DBCC UPDATEUSAGE command that I ran on one of the tables in my database.  

Note that I used the database name ‘LearnSQLWithBru‘ and the table ‘transaction_history‘ in the above example. 

The DBCC command can be run on a database to correct inaccuracies of all objects in that database or you can also correct the inaccuracies of a single table by including that table name. If you would like to run the command for a particular database, then you can run the following command..

DBCC UPDATEUSAGE ('DATABASENAME')

You can also run the below command to correct the inaccuracies for the current database.

DBCC UPDATEUSAGE (0)

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– Bru Medishetty

Using sp_delete_backuphistory to delete backup history

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You might be aware that system database msdb in SQL Server contains tables related to backup and restore operations of that Instance. Every time a database backup is performed, details regarding that backup is stored in multiple tables in msdb database. This information is useful when you want to restore a database to a point in time using the SQL Server Management Studio. But after certain period, the old data about the backups is not that useful anymore.  

It is common to have few dozens of databases on a SQL Server instance and when they are regularly backed up as part of being able to recover to a most recent point in time. Assuming the transaction log backups are scheduled at every 10 or 15 mins for most part of every day, the number of rows generated due to those backups would be slowly but surely adding up rows in those backup tables in msdb. In order to let database admins contain the size of msdb database, SQL Server provides a System Stored procedure called sp_delete_backuphistory to purge backup history from the underlying backup and restore tables in msdb.

The stored procedure accepts a date parameter @oldest_date. The stored procedure takes the value passed into that parameter and deletes the data in the backup and restore tables up to that date.  Let us assume you have never purged the backup information and the msdb database contains the backup information from the beginning of the SQL instance which was setup a couple of years back, the chances are the msdb database would be already huge in size (depends on how many db’s reside on the instance and how frequent the databases are backed up). In that situation, in order to delete all the backup history before 1/7/2011, you will have to pass the date value 1/7/2011 to the stored procedure as follows.

EXEC msdb.dbo.sp_delete_backuphistory @oldest_date = '1/7/2011'

It would be good to purge the backup history on a regular basis such as weekly or daily using a SQL Agent job.

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– Bru Medishetty

Installing SQL Server 2008 R2 Service Pack 1

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This blog will provide a step by step details of installing SQL Server 2008 R2 Service Pack 1. Before installing Service Pack, I would recommend you read one of my earlier blogs Best Practices for applying SQL Server Service Packs.

Once you have downloaded the Service Pack 1, copy the .exe file to a local drive and right click on the file and choose Open from the popup menu to begin the installation. (You can alternately double click the file to begin the installation).

The exe file take a min or two (depending on your system) and extracts to a temporary location, once the extraction is completed, the below screen is displayed and the installer performs few checks and displays the below screen. If there are any failures, ensure that the necessary steps are performed. Click Next to continue installation.

Accept the license terms by selecting the check box. In addition to accepting the license terms, you might chose if you would like Microsoft receive emails about the feature usage on your Instance. Click Next to proceed.

The next step is features selection, where you have to choose the components to which you would like to apply the Service Pack 1. We are going to apply SP1 for 2 instances at the same time. If you have more than 1 SQL 2008 R2 Instances on the machine, you can choose which instance(s) to apply Service Pack. You can select the check boxes beside each of the Instances or if you wish to Install for all Instances / features click Select All button in the bottom left.

You can click on the Instance to see the current details of that Instance / feature. In the picture below, I clicked on the R2_PRODINST and the Edition, Patch Level and other details are displayed..

Click Next after you are done selecting the features to be applied with SP1.

The next step checks for the files / services that are being used currently and lists if there are any files that needs to be stopped in order to avoid a restart. 

Click Next to proceed. Then the below screen is displayed which shows a summary of features that are going to be updated to Service Pack 1. Click Update to start the installation.

Once the Installation is done, the installation progress is displayed showing the list of Instances / features which were updated.. Click Next to continue.

Click Close to close the Service Pack Installer. Restart the machine if possible, else the SQL Instance(s) that have been updated with the Service Pack 1 (in case of multiple instances).

Do you like this site? Like our FB page @ Facebook.com\LearnSQLWithBru so that, you know when there is a new blog post.

– Bru Medishetty