Answering just: > What if a string to save is too large for a page? Then K is less than 1? What does K<1 means? From [B-tree Pages](https://sqlite.org/fileformat2.html#b_tree_pages): "Large keys on index b-trees are split up into overflow pages so that no single key uses more than one fourth of the available storage space on the page and hence every internal page is able to store at least 4 keys." Hence, K will never be less than 4 on those pages. (But see the paragraph beginning with "The number of keys on an interior b-tree page, K, ...".) As far as I can see from the clear file format documentation, K will never be less than one. Regarding: > It is not clear from the manual as the manual does not define what "K" is. This looks like a problem that should be fixed in the manual. Not so. See above quotation containing "K". Your problem diagnosis is premature and should be deferred until you have read the documentation much more carefully.