XQPCTLD1 controls multithreading, which can be used only
    by PATHWORKS servers. The default value of XQPCTLD1 is 8,
    which enables multithreading. Setting XQPCTLD1 to 0 disables
    multithreading,

    This special parameter is use by VSI and is subject to change. Do
    not change this parameter unless VSI recommends that you do so.