1) On success this method returns:

<UpdateCaseFields2Result>
	<Response>success</Response>
</UpdateCaseFields2Result>

2) In case of any errors this method returns:

<UpdateCaseFields2Result>
	<Response>fail</Response>
	<Errors>
		<UpdateError>
			<ErrorName>incorrectvalue</ErrorName>
			<ErrorField>A document class</ErrorField>
			<ErrorValue>HR document D1</ErrorValue>
		</UpdateError>
	</Errors>
</UpdateCaseFields2Result>

A list of returned error names in the <ErrorName/> tag:
- unauthorized: user not logged-in, a reason placed in <ErrorDescription/> tag;
- incorrectvalue: a wrong field value, a field name in <ErrorField/>, a wrong value in <ErrorValue/> tag;
- missingfield: there is no such field on the form, a wrong field name in <ErrorField/> tag;
- casenotopened: there is no such case or user has no rights, a reason placed in <ErrorDescription/> tag;
- updatefailed: an error has occured while updating case, a reason placed in <ErrorDescription/> tag;
- unexpected: an exception, a reason placed in <ErrorDescription/> tag.

A list of case errors that may appear in <ErrorDescription/> tag:
LOCK,
NO_MODIFY_PERMISSIONS,
ACTIVE_ACCEPTANCE,
NEXT_OWNER_NOT_ALLOWED,
NEXT_STATE_NOT_ALLOWED,
NEXT_OWNER_NOT_FOUND,
NEXT_STATUS_NOT_FOUND,
REQUIRED_PARAMETER_EMPTY,
REQUIRED_ATTACHMENT_MISSING,
REQUIRED_FORM_MISSING,
RULES_ERROR,
EDIT_LOCK.