A database query optimizer for a computer system having dynamically configurable logical partitions generates an optimized query strategy which is dependent on a logical partition configuration. Even if sequential inputoutput requests of the host are separated through a distribution processing to a plurality of paths, they are recognized on the device controller side and a countermeasure is taken. The differences of x and y coordinates and the sum of error E are computed, the integer part of \u0394x over \u0394y is denoted as Q. Methods are provided for manipulating fluids using the microfluidic device.