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PFN_COLOR_COUNT is a system parameter that specifies the number of buckets (colors) into which all members of the zeroed page list and all unencumbered members of the free page list are sorted. In is available on Alpha and Integrity systems only. OpenVMS Alpha systems might derive a preferred page color from a request to map a given virtual page and attempt to map that virtual page to a PFN of matching "color." This results in less variance in which cache blocks are used when accessing that page. This might or might not improve performance, depending on the application. This special parameter is use by VSI and is subject to change. Do not change this parameter unless VSI recommends that you do so. If you increase this parameter, you must also increase the ZERO_ LIST_HI system parameter.