APOLLO & ECW Q&A

[#1]

Symptoms

Some users found the following WCS GetCoverage request trigger "Null buffer" error.
When GetCoverage request small pixels (e.g., 1000x1000) there is no issue, but when request exceeds more than 4000x4000 pixels there is "ImageX returned a null buffer for the supplied request, there are no pixels to process!" error

http://<apollo>/erdas-apollo/coverage_public/EAIM?request=GetCoverage&service=WCS&version=2.0.1&coverageid=testimage&FORMAT=image/tiff&SCALESIZE=X(5000),Y(5000)&rangesubset=band1,band2,band3

<ows:ExceptionReport xsi:schemaLocation="http://www.opengis.net/ows/2.0 http://schemas.opengis.net/ows/2.0/owsExceptionReport.xsd" version="2.0.1"><ows:Exception exceptionCode="NoApplicableCode" locator="ImageX returned a null buffer for the supplied request, there are no pixels to process!"/></ows:ExceptionReport>

Diagnosis

The "Null buffer" error means Apollo run out of memory

Solution

Increase RDS Xmx memory
"Data Manager -> Configuration 64 bit RDS tune up parameters -> Xmx"

Decrease Large Output Trigger (e.g., change from 7000 to 2700), so Apollo will not require much memory for WCS request
"Data Manager -> Services > Raster > EAIM > Edit Provider > Data Source > Large Output Trigger"