This feature will be removed in a future version of Microsoft SQL Server. Do not use this feature in new development work, and modify applications that currently use this feature as soon as possible. Use CLR Integration instead.
Microsoft SQL Server loads an extended stored procedure DLL as soon as a call is made to one of the functions of the DLL. The DLL remains loaded until the server is shut down or until the system administrator uses the DBCC statement to unload it. For example, this command unloads the xp_hello.dll, allowing the system administrator to copy a newer version of this file to the directory without shutting down the server: