Seaquel
SQL Server error code

SQL Server error 9535

SQL Server raises error 9535 at severity 16, which marks a problem with the query or data that you can correct.

For untyped XML it is not allowed to specify MAXLENGTH or SINGLETON option if XSD type is not already specified for path '%.*ls' of selective XML index '%.*ls'.
Msg9535
Severity16
Group9000–9999

Source: Database Engine events and errors