clr enabled Server Configuration Option

THIS TOPIC APPLIES TO:yesSQL Server (starting with 2008)noAzure SQL DatabasenoAzure SQL Data Warehouse noParallel Data Warehouse

Use the clr enabled option to specify whether user assemblies can be run by SQL Server. The clr enabled option provides the following values:

Value Description
0 Assembly execution not allowed on SQL Server.
1 Assembly execution allowed on SQL Server.

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 hierarchy data type, replication, and Policy-Based Management.


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 SQL Server 2017, 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. SQL Server 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.


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';  

See Also

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