normally ansys arranges himself.
do not increase the visual memory of windows because it is counterproductive. better than its value is reduced.
when ansys part controls whether it manages to launch all analysis in ram memory (solution "in-core"). if it does not exist then it goes in "out-of-core", loads in ram some portions of the solution while the others go in a ".page" file created automatically that represents the visual memory.
Note: When you launch the solution in ansys messages indicates the "minimum out of core memory", i.e. the minimum ram required to start the solution.