Q: BTscanner - range scan savings

Hello everyone. Following one of the recent threads I read about BTscanner and how it works. Then I checked its output and found out potential place for optimization. Or maybe I'm just misinterpreting the output. The problem is that "onstat -C range" reports many 100% (or close) savings if range scanning is used. A part of the output follows at the end of the post. My question is: based on the output, how do I calculate range threshold that should be set (it's currently disabled) to improve index performance? Thanks everyone. P.S. I recently restarted the instance, plus now it's period of very low user activity so the numbers aren't representative, but still I'm curious about the formula for range threshold. > onstat -C range IBM Informix Dynamic Server Version 9.40.UC5W2 -- On-Line -- Up 2 days 22:52:42 -- 1917952 Kbytes Btree Cleaner Info Cleaning Range Statistics ========================= Partnum Key Low High Size Saving 0x00100002 1 1 1 4 100.0 % 0x00200005 1 6214 6375 8016 98.0 % 0x00200005 2 743 6440 8016 28.9 % 0x00200007 1 92 92 2508 100.0 % 0x00200009 1 37 61 1008 97.6 % 0x00200009 2 66 66 1008 100.0 % 0x0020000d 1 14 14 1008 100.0 % 0x0020000d 2 10 10 1008 100.0 % 0x00200011 2 569 569 10064 100.0 % 0x00200011 3 93 741 10064 93.6 % 0x00200014 1 1802 1927 10032 98.8 % 0x00200014 2 2307 8880 10032 34.5 % 0x0020001a 1 5 5 508 100.0 % 0x0020002d 1 50 251 508 60.4 % 0x0020002d 2 20 131 508 78.1 % 0x0020003a 1 540 1016 1386 65.7 % 0x00200048 1 1 1 18 100.0 % 0x00200049 1 1 1 28 100.0 % 0x0020004f 1 4 103 3906 97.5 % 0x00200050 1 5 24 1375 98.6 % 0x00200052 1 7 61 2875 98.1 % 0x00200054 1 26 26 36 100.0 % 0x00200055 1 3 6 8 62.5 % 0x0020005c 1 2 4 129 98.4 % 0x0020005d 1 1 1 70 100.0 % 0x0020006f 1 2 6 20 80.0 % 0x00200070 1 1 1 14 100.0 % 0x00200072 1 2 3 6 83.3 % 0x00200073 1 2 9 36 80.6 % 0x00200074 1 3 6 20 85.0 % 0x00200076 1 3 4 25 96.0 % 0x002000d8 1 7 7 277 100.0 % 0x002000dc 1 2 2 120 100.0 % 0x002000dd 1 2 3 156 99.4 % 0x002000de 1 2 3 132 99.2 % 0x002000e0 1 8 8 247 100.0 % 0x002000e2 1 6 6 296 100.0 % 0x002000e4 1 1 1 129 100.0 % 0x002000e5 1 3 3 140 100.0 % 0x002000e7 1 1 1 118 100.0 % 0x002000e8 1 6 6 294 100.0 % 0x002000ed 1 1 1 140 100.0 % ...