InventoryOnhand AIF Question (Ax2009 AP1)

im getting folowing error when i call READ method of Inventoryonhand AIF service

“itemid is not a field in data source inventsum”

iam using SOAP Ui and below is the request . I have tried Inventdimid also as it is one of index fields.,

<soapenv:Envelope xmlns:soapenv="">schemas.xmlsoap.org/…/" xmlns:ser="">schemas.microsoft.com/…/services" xmlns:quer="">schemas.microsoft.com/…/QueryCriteria">

soapenv:Header/

soapenv:Body

ser:InventoryOnHandService_basicFindKeysRequest

quer:QueryCriteria

quer:CriteriaElement

quer:DataSourceNameinventsum</quer:DataSourceName>

quer:FieldNameitemid</quer:FieldName>

quer:OperatorEQUAL</quer:Operator>

quer:Value102113001429</quer:Value1>

</quer:CriteriaElement>

</quer:QueryCriteria>

</ser:InventoryOnHandService_basicFindKeysRequest>

</soapenv:Body>

</soapenv:Envelope>

Please help