Calculating table sizes, index pages, extents

We're trying to make some extent related calculations for our databases, and I'm using the stuff in Chapter 10 or "Informix Guide to SQL: Tutorial" (dated December 1991) as a guide. (I'm actually writing a perl script to do the calculations.) Unfortunately, there are some discrepancies between the descriptions and the examples in that chapter. I wanted to check here to see whether anyone knew anymore about it. The discrepancies occur on the subsection "Estimating Index Pages" (pages 10-16 to 10-17 in my copy) of the section "Calculating Table Sizes" (which begins on page 10-12). There are two of them there: 1. In the text (on page 10-16), when describing the index entry size (which they call "entsize"), they say it needs a 4 byte pointer, so they define entsize = (keysize * pctuniq) + 4 But in the examples (on page 10-17), they add 8, not 4, to get entsize. 2. Earlier in the section (page 10-12), they define pageuse = pagesize - 28 Since pagesize is normally 2048, that means pageuse should be 2020. But in the examples on page 10-17, they have pageuse = 2016. The previous two examples in the section did have pageuse = 2020. Anyone know what's going here? Thanks for any help. -- Milt Epstein Visiting Research Programmer National Animal Poison Control Center (NAPCC) epstein@napcc-hp.cvm.uiuc.edu College of Veterinary Medicine (CVM) (or mepstein@uiuc.edu) University of Illinois at Urbana-Champaign (UIUC)