With CM KSAM files, the HP program Ksamutil used to show the number of
levels of the B-Tree index.  Does anyone know if there is a way of
producing this information for NM Ksam files?

Are there any "rules of thumb" about how the efficiency of a program
degrades as an NM Ksam file becomes full as there is for Image Master
Files (i.e. preferably <66% full)

For example, I have a program (inherited, old but working) which links
from a KSAM file into an Image database.  The KSAM file has about 600,000
records in it and a capacity of 690,000.  The program runs for 399 cpu
secs for the specified selection.  If the KSAM file is then rebuilt so
that the 600,000 now exist in a file of capacity 900,000, then the same
selection reduces to 360 cpu secs.

This sort of reduction seems to apply on many databases when the KSAM
file is resized.
Are there any rules,  is the number of levels of B-tree relevant or not?
 Is there anything else (in terms of structure) that I should consider.

Any comments gratefully appreciated.