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configure-the-locks-server-configuration-option.md

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title Configure the locks Server Configuration Option | Microsoft Docs
description Learn about the locks option. See how to use it to limit the amount of memory that the SQL Server Database Engine uses for locks.
ms.custom
ms.date 03/02/2017
ms.prod sql
ms.prod_service high-availability
ms.reviewer
ms.technology configuration
ms.topic conceptual
helpviewer_keywords
locks option [SQL Server]
ms.assetid b0cf0f86-7652-4574-a9fb-908e10d03973
author markingmyname
ms.author maghan

Configure the locks Server Configuration Option

[!INCLUDE SQL Server]

This topic describes how to configure the locks server configuration option in [!INCLUDEssnoversion] by using [!INCLUDEssManStudioFull] or [!INCLUDEtsql]. The locks option sets the maximum number of available locks, thereby limiting the amount of memory the [!INCLUDEssDEnoversion] uses for them. The default setting is 0, which allows the [!INCLUDEssDE] to allocate and deallocate lock structures dynamically, based on changing system requirements.

Important

[!INCLUDEssNoteDepFutureDontUse]

In This Topic

Before You Begin

Recommendations

  • This option is an advanced option and should be changed only by an experienced database administrator or certified [!INCLUDEssNoVersion] professional.

  • When the server is started with locks set to 0, the lock manager acquires sufficient memory from the [!INCLUDEssDE] for an initial pool of 2,500 lock structures. As the lock pool is exhausted, additional memory is acquired for the pool.

    Generally, if more memory is required for the lock pool than is available in the [!INCLUDEssDE] memory pool, and more computer memory is available (the max server memory threshold has not been reached), the [!INCLUDEssDE] allocates memory dynamically to satisfy the request for locks. However, if allocating that memory would cause paging at the operating system level (for example, if another application is running on the same computer as an instance of [!INCLUDEssNoVersion] and using that memory), more lock space is not allocated. The dynamic lock pool does not acquire more than 60 percent of the memory allocated to the [!INCLUDEssDE]. After the lock pool has reached 60 percent of the memory acquired by an instance of the [!INCLUDEssDE], or no more memory is available on the computer, further requests for locks generate an error.

    Allowing [!INCLUDEssNoVersion] to use locks dynamically is the recommended configuration. However, you can set locks and override the ability of [!INCLUDEssNoVersion] to allocate lock resources dynamically. When locks is set to a value other than 0, the [!INCLUDEssDE] cannot allocate more locks than the value specified in locks. Increase this value if [!INCLUDEssNoVersion] displays a message that you have exceeded the number of available locks. Because each lock consumes memory (96 bytes per lock), increasing this value can require increasing the amount of memory dedicated to the server.

  • The locks option also affects when lock escalation occurs. When locks is set to 0, lock escalation occurs when the memory used by the current lock structures reaches 40 percent of the [!INCLUDEssDE] memory pool. When locks is not set to 0, lock escalation occurs when the number of locks reaches 40 percent of the value specified for locks.

Security

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.

Using SQL Server Management Studio

To configure the locks option

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

  2. Click the Advanced node.

  3. Under Parallelism, type the desired value for the locks option.

    Use the locks option to set the maximum number of available locks, thereby limiting the amount of memory [!INCLUDEssNoVersion] uses for them.

Using Transact-SQL

To configure the locks option

  1. Connect to the [!INCLUDEssDE].

  2. From the Standard bar, click New Query.

  3. Copy and paste the following example into the query window and click Execute. This example shows how to use sp_configure to set the value of the locks option to set the number of locks available for all users to 20000.

Use AdventureWorks2012 ;  
GO  
sp_configure 'show advanced options', 1;  
GO  
RECONFIGURE;  
GO  
sp_configure 'locks', 20000;  
GO  
RECONFIGURE;  
GO

For more information, see Server Configuration Options (SQL Server).

Follow Up: After you configure the locks option

The server must be restarted before the setting can take effect.

See Also

RECONFIGURE (Transact-SQL)
Server Configuration Options (SQL Server)
sp_configure (Transact-SQL)