On Sat, Sep 7, 2013 at 8:15 AM, Kjell Rilbe <kjell.rilbe@...> wrote:

I'm considering if "use all space" would be a good idea or not. I think
I understand its effect on indices: fill index pages completely vs.
leave 25% free space on each index page for new entries.

Unh, no.  Use All Space affects only data pages.  Index pages are filled

completely when an index is created after the data is stored - as gbak

does.  They're also pretty thoroughly filled if data is inserted in key order.

When data is stored in random order, index pages tend to average 60-70%

full.  That's because the index page split code leaves half the entries on

the old page and puts half on the new page, unless the new entry would

be the last entry on the page.  If the new entry would be last, only it goes

on the new page.  (90% certainty on that).

So Use All Space has no effect on indexes, but will make data updates

and deletes expensive.

Good luck,

Ann