Can not get plane data when resolution=0 and fixedResolution=true

[East2010]

I want to get data along a time slice,when the resolution=0 and fixedResolution=true,the program will wait forever.

SbBox3i32 box(SbVec3i32(0,0,0),SbVec3i32(RvolData->data.getSize()[0],RvolData->data.getSize()[1],RvolData->data.getSize()[2]));
SoVolumeData::LDMDataAccess::DataInfoPlane info;
SoBufferObject* dummyPtr = NULL;
info = RvolData->getLdmDataAccess().getData( 0, box, plane, dummyPtr );
		

SoCpuBufferObject *cpuBufferObject = new SoCpuBufferObject;

cpuBufferObject->setSize(info.bufferSize);
info = RvolData->getLdmDataAccess().getData( 0, box, plane, cpuBufferObject );//Here will program wait forever
if (info.errorFlag == SoVolumeData::LDMDataAccess::CORRECT)
{
   //process data
}

To get the data,first I change the fixedResolution of RvolData to false,after read,change it to true.It is ok.
But I want to know why the program wait forever.