Following are the common error message during oracle xml report.

1. XML document must have a top level element. Error processing resource.
2. The file should be in XML-DATA-TEMPLATE format.
3. ora-00911 invalid character in oracle xml.
4.The following tags were not closed.

Points to resolve the above issue:

1. write the first line as "<?xml version="1.0" encoding="UTF-8"?>". Write it in the same format without changing the case of any words.

2. write 'dataTemplate' as 'dataTemplate'. It may give error during generating output xml file if we write like, Datatemplate or DATATEMPLATE or datatemplate.

3.Close the tags properly. Take care of  /> closing tags.

4.<sqlStatement name> and <group source> must have same value.

5.The parameter name must be exactly like token name or bind variable name. (including the case of the variables).

6.The <element value > must be same to the column name.

7.Check the dataType of the parameter.

Following image will provide the proper format for data template xml file: