Regarding (b): In KNIME Analytics Platform 3.6.1 and earlier, only parts of the data are deleted right after the data transfer. Most of it is deleted when KNIME closes properly. This behavior was fixed in the meantime and will be part of the next release of KNIME AP. @mereep, please feel free to try it out using our nightly build (please see the disclaimer there). We’d highly appreciate any feedback on whether that mitigates the problem 
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