creates an XML serialization assembly for types in a specified assembly in order to improve the startup performance of a XmlSerializer when it serializes or deserializes objects of the specified types.
UNSAFE ? Code executed by an assembly with SAFE permissions cannot access external system resources such as files, the network, environment variables, or the registry and EXTERNAL_ACCESS can access. UNSAFE enables assemblies unrestricted access to resources, both within and outside an instance of SQL Server. Code running from within an UNSAFE assembly can call unmanaged code.