Informix 7.1.2.UC1: LRUS in /usr/informix/etc/onconfig

The On-Line manual on page 12-36 says LRUS should be either 4 or the number of virtual cpus -- this is a very low number. Most of the Informix Press tuning books and chapters on tuning, say LRUS should be equal to CLEANERS and shouldn't be too small. This is typically a higher number. Who is right? Why the difference? On an interactive time-sharing system attempting to service many user's interactive GUI queries, what is the disadvantage of setting LRU's too low? Could a low LRU be tied to a longer checkpoint duration? That is, if LRU_MIN_DIRTY and LRU_MAX_DIRTY are both held constant, say 5 and 7 respectively, does a higher or lower LRU result in a shorter checkpoint duration? I want the absolute bare minimum checkpoint duration of one or two seconds long on a SparcCenter 1000e with 768mb of memory, 6 cpus, 4 Sparc Storage Arrays having 30 disks each. So far, setting LRU_MIN_DIRTY and LRU_MAX_DIRTY down to 5 and 7 respectively, with CLEANERS at 29 and LRU at 5 (LRU formerlyl at 16) has resulted in approximately 1/5th the checkpoint durations of when CLEANERS was at 29 and LRU was at 16 and LRU_MIN_DIRTY was at 55 and LRU_MAX_DIRTY was at 60. But I'd like to get it down another factor of 2. Right now, my checkpoint durations are at 5-10 seconds which is just at the outside limit of tolerable interactive response in a GUI. It really isn't responsive. I can't have a checkpoint interrupt a user's GUI query to the database engine and slow it down by 5-10 seconds. Hence my search for the "mythical" 1-2 second checkpoint. Your thoughts on LRU variable? Other relevant variables? --Stuart