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Server configuration: min memory per query

  • Artikkeli

Applies to: SQL Server

This article describes how to configure the min memory per query server configuration option in SQL Server by using SQL Server Management Studio or Transact-SQL. The min memory per query option specifies the minimum amount of memory (in kilobytes) to allocate for the execution of a query. This is also known as the minimum memory grant. For example, if min memory per query is set to 2,048 KB, the query is guaranteed to get at least that much total memory. The default value is 1,024 KB. The minimum value 512 KB, and the maximum is 2,147,483,647 KB (2 GB).

Limitations

The amount of min memory per query has precedence over the index create memory option. If you modify both options and the index create memory is less than min memory per query, you receive a warning message, but the value is set. During query execution, you receive another similar warning.

Recommendations

This option is an advanced option and should be changed only by an experienced database administrator or certified SQL Server professional.

The SQL Server query processor tries to determine the optimal amount of memory to allocate to a query. The min memory per query option lets the administrator specify the minimum amount of memory any single query receives. Queries generally receive more memory than this, if they have hash and sort operations on a large volume of data. Increasing the value of min memory per query might improve performance for some small to medium-sized queries, but doing so could lead to increased competition for memory resources. The min memory per query option includes memory allocated for sort operations.

Don't set the min memory per query server configuration option too high, especially on very busy systems, because the query has to wait1 until it can secure the minimum memory requested, or until the value specified in the query wait server configuration option is exceeded. If more memory is available than the specified minimum value required to execute the query, the query is allowed to make use of the extra memory, if the memory can be used effectively by the query.

1 In this scenario, the wait type is typically RESOURCE_SEMAPHORE. For more information, see sys.dm_os_wait_stats.

Permissions

Execute permissions on sp_configure with no parameters or with only the first parameter are granted to all users by default. To execute sp_configure with both parameters to change a configuration option or to run the RECONFIGURE statement, a user must be granted the ALTER SETTINGS server-level permission. The ALTER SETTINGS permission is implicitly held by the sysadmin and serveradmin fixed server roles.

Use SQL Server Management Studio

  1. In Object Explorer, right-click a server and select Properties.

  2. Select the Memory node.

  3. In the Minimum memory per query box, enter the minimum amount of memory (in kilobytes) to allocate for the execution of a query.

Use Transact-SQL

  1. Connect to the Database Engine.

  2. From the Standard bar, select New Query.

  3. Copy and paste the following example into the query window and select Execute. This example shows how to use sp_configure to set the value of the min memory per query option to 3500 KB.

    USE master;
GO

EXECUTE sp_configure 'show advanced options', 1;
GO

RECONFIGURE;
GO

EXECUTE sp_configure 'min memory per query', 3500;
GO

RECONFIGURE;
GO

EXECUTE sp_configure 'show advanced options', 0;
GO

RECONFIGURE;
GO

Follow up: After you configure the min memory per query option

The setting takes effect immediately without restarting the server.

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