I am trying to compute raster zonal statistics using a TIFF and shp file. I am using WPS process extension for geoserver. I am trying to use the WPS request builder provided by my GeoServer installation under demos. I am trying to execute the process to see the output but I am getting the message in the second screenshot. My geoTiff file is 459 MB. Am I doing something wrong? 

The following are the screenshots:

[![enter image description here][1]][1].

[![enter image description here][2]][2]


The following is the xml output generated by clicking the "Generate xml from process I/O":

 <?xml version="1.0" encoding="UTF-8"?><wps:Execute version="1.0.0" service="WPS" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wps/1.0.0" xmlns:wfs="http://www.opengis.net/wfs" xmlns:wps="http://www.opengis.net/wps/1.0.0" xmlns:ows="http://www.opengis.net/ows/1.1" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xmlns:wcs="http://www.opengis.net/wcs/1.1.1" xmlns:xlink="http://www.w3.org/1999/xlink" xsi:schemaLocation="http://www.opengis.net/wps/1.0.0 http://schemas.opengis.net/wps/1.0.0/wpsAll.xsd">
 <ows:Identifier>ras:RasterZonalStatistics</ows:Identifier>
 <wps:DataInputs>
 <wps:Input>
 <ows:Identifier>data</ows:Identifier>
 <wps:Reference mimeType="image/tiff" xlink:href="http://geoserver/wcs" method="POST">
 <wps:Body>
 <wcs:GetCoverage service="WCS" version="1.1.1">
 <ows:Identifier>soil_system:PI</ows:Identifier>
 <wcs:DomainSubset>
 <ows:BoundingBox crs="http://www.opengis.net/gml/srs/epsg.xml#4326">
 <ows:LowerCorner>-128.14691380352517 22.714877523496572</ows:LowerCorner>
 <ows:UpperCorner>-65.08558771879018 51.75931655065378</ows:UpperCorner>
 </ows:BoundingBox>
 </wcs:DomainSubset>
 <wcs:Output format="image/tiff"/>
 </wcs:GetCoverage>
 </wps:Body>
 </wps:Reference>
 </wps:Input>
 <wps:Input>
 <ows:Identifier>zones</ows:Identifier>
 <wps:Reference mimeType="text/xml" xlink:href="http://geoserver/wfs" method="POST">
 <wps:Body>
 <wfs:GetFeature service="WFS" version="1.0.0" outputFormat="GML2" xmlns:soil_system="soil_system">
 <wfs:Query typeName="soil_system:USA_States_WGS84"/>
 </wfs:GetFeature>
 </wps:Body>
 </wps:Reference>
 </wps:Input>
 <wps:Input>
 <ows:Identifier>classification</ows:Identifier>
 <wps:Reference mimeType="image/tiff" xlink:href="http://geoserver/wcs" method="POST">
 <wps:Body/>
 </wps:Reference>
 </wps:Input>
 </wps:DataInputs>
 <wps:ResponseForm>
 <wps:RawDataOutput mimeType="text/xml; subtype=wfs-collection/1.0">
 <ows:Identifier>statistics</ows:Identifier>
 </wps:RawDataOutput>
 </wps:ResponseForm>
 </wps:Execute>

 [1]: https://i.sstatic.net/4y3qk.png
 [2]: https://i.sstatic.net/c9iGZ.png