Subject Re: [firebird-support] Use all space or not on large restore?
Author Ann Harrison
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,