Using extended stored procedures or SP_OA stored procedures to load CLR in SQL Server is not supported

Original product version:   SQL Server
Original KB number:   322884


SQL Server 2005 and later versions host Common Language Runtime (CLR) and support procedures, functions, triggers, types, and aggregates that are written in CLR languages. In these versions, you cannot load CLR by using extended stored procedures or sp_OA stored procedures.

Original product version:   SQL Server
Original KB number:   322884

More information

The .NET Framework assembly System.Runtime.InteropServices provides a robust environment for invoking assemblies from unmanaged code. However, there are several technical discordances between the internal implementations of CLR and SQL Server:


To increase performance, the CLR implements Thread Local Storage.

Additionally, CLR uses only thread-based scheduling and does not support Fiber-mode scheduling. However, SQL Server can use Fiber-mode scheduling. To configure this property, run the sp_configure stored procedure by using the lightweight pooling option. For more information about this topic, review lightweight pooling Server Configuration Option.


The use of extended stored procedures and OLE Automation both run in the virtual memory address space of the memory of SQL Server. The default SQL Server memory is only a fraction of the memory that SQL Server can potentially use and CLR competes with any existing implementations for these memory resources.

COM interoperability

This section specifically addresses the use of OLE Automation in SQL Server and it applies to both in-process and out-of-process COM objects. Assembly meta data for function interfaces implements a typed mechanism for any invocations.

As part of this design, the COM Callable wrapper for an assembly must use an external mechanism of mapping a ClassID to a member of a managed class. Because of this explicit mapping, there is no ability from an unmanaged perspective to establish a root list of available interfaces.

The extended stored procedure sp_oaCreate uses the IUnknown::QueryInterface interface to determine the object's support for a particular interface. The interoperability between CLR and unmanaged code relies on the IDispatch interface for implementing interfaces. Because there is no equivalent to a QueryInterface method to a CLR-based assembly, you cannot create an instance of the object.