A method for cleaning tubes and heat exchangers provides a cavitation enhancement unit between a source of pressurized fluid an a lance. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this abstract. Medial and lateral adjustable length struts couples medial and lateral portions of the first fixation ring to medial and lateral portions of the second fixation ring respectively, each of the medial and lateral adjustable length struts including a constrained hinge joint. Both point-in-time copy relationships are established and any continuous synchronous copy requirements of the volume swap relationship between the first point-in-time target volume and the second point-in-time target volume are disabled.