There is a 2 GB limit on the size of XML documents. If you request a document in an encoding that results in a document larger than 2 GB, an error is raised. For example, you may have a large document encoded in ASCII which is 1.5 GB and fits under the 2 GB limit. However, if you request a serialization with UTF-16 encoding, the size of such an encoding would be larger than the 2GB limit because UTF-16 is a double-byte encoding, and this would result in an error.