clr-enabled-server-configuration-option.md

title	clr enabled Server Configuration Option | Microsoft Docs
description	Learn how to use the clr enabled option to specify whether SQL Server can run user assemblies. See when common language runtime execution is not supported.
ms.custom
ms.date	06/20/2017
ms.prod	sql
ms.prod_service	high-availability
ms.reviewer
ms.technology	configuration
ms.topic	conceptual
helpviewer_keywords	assemblies [CLR integration], verifying can run clr enabled option
ms.assetid	0722d382-8fd3-4fac-b4a8-cd2b7a7e0293
author	markingmyname
ms.author	maghan

clr enabled Server Configuration Option

[!INCLUDE SQL Server]

Use the clr enabled option to specify whether user assemblies can be run by [!INCLUDEssNoVersion]. The clr enabled option provides the following values:

Value	Description
0	Assembly execution not allowed on [!INCLUDEssNoVersion].
1	Assembly execution allowed on [!INCLUDEssNoVersion].

WOW64 only. Restart WOW64 servers to effect the settings changes. No restart required for other server types.

When you run RECONFIGURE, and the run value of the clr enabled option is changed from 1 to 0, all application domains containing user assemblies are immediately unloaded.

Common language runtime (CLR) execution is not supported under lightweight pooling Disable one of two options: "clr enabled" or "lightweight pooling". Features that rely upon CLR and that do not work properly in fiber mode include the hierarchyid data type, the FORMAT function, replication, and Policy-Based Management.

[!WARNING] CLR uses Code Access Security (CAS) in the .NET Framework, which is no longer supported as a security boundary. A CLR assembly created with PERMISSION_SET = SAFE may be able to access external system resources, call unmanaged code, and acquire sysadmin privileges. Beginning with [!INCLUDEsssql17], an sp_configure option called clr strict security is introduced to enhance the security of CLR assemblies. clr strict security is enabled by default, and treats SAFE and EXTERNAL_ACCESS assemblies as if they were marked UNSAFE. The clr strict security option can be disabled for backward compatibility, but this is not recommended. Microsoft recommends that all assemblies be signed by a certificate or asymmetric key with a corresponding login that has been granted UNSAFE ASSEMBLY permission in the master database. [!INCLUDEssNoVersion] administrators can also add assemblies to a list of assemblies, which the Database Engine should trust. For more information, see sys.sp_add_trusted_assembly.

Example

The following example first displays the current setting of the clr enabled option and then enables the option by setting the option value to 1. To disable the option, set the value to 0.

EXEC sp_configure 'clr enabled';  
EXEC sp_configure 'clr enabled' , '1';  
RECONFIGURE;    

See Also

lightweight pooling Server Configuration Option
Server Configuration Options (SQL Server)
sp_configure (Transact-SQL)
lightweight pooling Server Configuration Option