The smaller of 1/20th of physical memory in pages and 100.
1 to fastscan / 2
Yes, unless dynamic reconfiguration operations that add or delete memory occur. At that point, the value is reset to whatever was provided in the /etc/system file or was calculated from the new physical memory value.
If slowscan is larger than fastscan / 2, slowscan is reset to fastscan / 2. No message is displayed.
When more aggressive scanning of memory is desired during periods of memory shortfall especially if the system is subject to periods of intense memory demand.