SQL Server 2008 R2 : Setting Database Options

Auto Options

Cursor Options

Database Availability Options

Date Correlation Optimization Options

External Access Options

Parameterization Options

Recovery Options

Service Broker Options

Snapshot Isolation Options

SQL Options

The following section focuses on the database options displayed on the Options page in SSMS.

The Database Options

You can access many of the most common database options via the Options page of the Database Properties dialog. To get to this dialog, you right-click a database in the SSMS Object Explorer and select Properties. When the dialog appears, you select the Options page from the list on the left side of the Database Properties dialog. Figure 1 shows the Options page for the AdventureWorks2008 database. The options listed under Other Options can be listed alphabetically or by category. The default display mode is by category.

Figure 1. Database options in SSMS.

The default settings for these options suffice for most installations. However, some options deserve special attention. The options listed under the Automatic category are among these options. The Auto Close option could cause problems in prior versions of SQL Server. This option is intended for desktop implementations in which the database does not need to be online all the time. When users are not accessing the database and this option is selected, the database files are closed. When the first user accesses the database, the database is brought back online. The problem in prior versions was that the synchronous operation of opening and closing the database files caused performance problems. This issue has been addressed in SQL Server 2008 because the operations are now performed asynchronously. The Auto Close option defaults to true only for SQL Server 2008 Express Edition and should generally be left set to false for all other versions.

The Auto Create Statistics and Auto Update Statistics options also deserve special attention in situations in which the creation or updating of statistics is affecting performance. Generally, the creation or updating of statistics improves performance. These statistics enable the Query Optimizer to make the best decisions when determining the access path to the data. In some rare circumstances, there may be performance problems at the time statistics are created or updated automatically. When these situations arise, you can turn off the Auto Statistics options and schedule the statistics operations to occur during off-hours.

Enabling the Auto Shrink option is a good idea for keeping a nonproduction database as small as possible. This option automatically performs a database shrink operation against the database files when more than 25% of a file contains unused space. The default setting is false because this option can cause performance problems (related to the timing of the shrink operation) in a production database. Because the operation is automatic, it can run at any time, including times when there may be heavy production load.

The Page Verify option in the Recovery category was enhanced in SQL Server 2005. That enhancement came in the form of a new CHECKSUM option. This CHECKSUM option is the default; it causes a checksum calculation to occur across the entire database page. Prior to the availability of the CHECKSUM option, page verification was done with TORN_PAGE_DETECTION. Both of these options help detect damaged database pages, but CHECKSUM is the method that Microsoft recommends. The CHECKSUM calculation can be complicated but it basically tells SQL Server to calculate a number based on the contents of each data / index page. The CHECKSUM value is stored in the page header when it is written to disk. When the page is read from the disk, the checksum is computed again and compared to the value in page header to help ensure that the contents of each page are valid.

Database Read-Only and Restrict Access are two other commonly used options in the State category. You can set Database Read-Only to true to prevent updates from occurring in the database. Databases used for reference and not updated are perfect candidates for this option. The Restrict Access options are handy when you’re executing system maintenance or mass updates in which you want to restrict users from accessing the database. Single User allows only one user to access the database. The Restricted option allows only members of db_owner, dbcreator, and sysadmin to access the database. With the Restricted option, there is no limit on the number of users in these groups that can access the database.

You can easily set up the options reviewed in this section as well as the other options mentioned by using the Database Properties dialog. The current value for each option is shown in the right-hand column. To set an option to another value, you click the current value, and a drop-down arrow appears. When you click the drop-down arrow, you can select from the list of valid values for the option. After making all your option changes, you can click OK for the changes to take effect immediately, or you can click the Script button to generate the T-SQL code to change the options. The T-SQL code used to change the options is discussed in the next section.

Using T-SQL to Set Database Options

If you prefer to use T-SQL, or if the option you need to set doesn’t appear in the Database Properties dialog, you can use the ALTER DATABASE command to set options. For example, the following command sets AUTO_UPDATE STATISTICS to OFF in the AdventureWorks2008 database:

ALTER DATABASE [AdventureWorks2008] SET AUTO_UPDATE_STATISTICS OFF WITH NO_WAIT


					  

You can also change some of the options by using the system stored procedure sp_dboption. This feature is scheduled to be removed in a future release of SQL Server but is still available in this release. You might still be using this procedure based on prior releases, and old habits are hard to break. Following is an example of one of the sp_dboption commands many people have been using for years:

EXEC sp_dboption 'AdventureWorks2008', 'single user', 'TRUE'

This command sets the AdventureWorks2008 database to single-user mode. Setting a database to single-user mode is useful when you’re performing certain database operations. For example, you might use sp_dboption to set a database to single-user mode prior to renaming the database with the sp_renamedb system procedure. It is important to break old habits and move on to using the ALTER DATABASE command. The single-user option and database name change have both been integrated into the ALTER DATABASE syntax. The following example shows how to set the single-user mode option and change the database name by using ALTER DATABASE:

ALTER DATABASE [AdventureWorks2008] SET  SINGLE_USER WITH NO_WAIT
GO
ALTER DATABASE [AdventureWorks2008] MODIFY NAME = [AdventureWorks2008_New]
GO

As you can see, using ALTER DATABASE is fairly straightforward and offers a consistent approach for modifying a database and its options.

ALTER DATABASE [AdventureWorks2008] SET OFFLINE WITH NO_WAIT

ALTER DATABASE [AdventureWorks2008] SET emergency WITH NO_WAIT.

Retrieving Option Information

You can retrieve database settings by using several different methods. You can use the Database Properties dialog in SSMS to display commonly accessed options. You can also use the DATABASEPROPERTYEX function or the sp_dboption system stored procedure to display individual database options. As mentioned previously, sp_dboption is slated for removal in a future release, so the DATABASEPROPERTYEX function is preferred. This function accepts input values for the database name and the option for which you want to retrieve the value. The following is an example of a SELECT statement you can use to retrieve the Auto Shrink option for the AdventureWorks2008 database:

SELECT DATABASEPROPERTYEX ('AdventureWorks2008', 'IsAutoShrink')

This function returns a value of 1 or 0 for Boolean values—with 1 being “on” or “true”—and returns the actual value for non-Booleans. Table 1 lists the valid properties for the DATABASEPROPERTYEX function.

If you would like to retrieve all the options set for a database, you have a couple of choices. The option that has been around for a while is sp_helpdb. You can pass to this system stored procedure the database name, and it returns several pieces of information about the database, including the options set. The database options are returned in the first result set from sp_helpdb in a column named Status. The database options are displayed in a comma-delimited format in the Status column. All Boolean options that are set to ON are returned in the Status column, and all non-Boolean values are returned with the value to which they are set.

The syntax for sp_helpdb is as follows:

sp_helpdb database_name

The sys.databases catalog view is another good resource for displaying all the database options. This catalog view has a separate column for each of the database options and is much easier to read than the sp_helpdb output. The view also has the added flexibility of allowing you to choose a set of options to return. The following example shows a SELECT statement that uses the sys.databases catalog view to return a common set of options:

select name, is_auto_close_on, is_auto_shrink_on,
    is_auto_create_stats_on, is_auto_update_stats_on
from sys.databases
where name = 'AdventureWorks2008'

The results from this SELECT statement return Boolean values in each column, indicating whether the option is set to on or off. The number of columns available for selection is extensive and similar to those options available with the DATABASEPROPERTYEX function.