Re: Freelists

"Keith Boulton" <kboulton_at_ntlunspam-world.com> wrote in message news:<QTOc7.9766$zs.55688_at_news11-gui.server.ntli.net>...
> "Mark D Powell" <mark.powell_at_eds.com> wrote in message
> news:178d2795.0108080539.3bf61f2e_at_posting.google.com...
> > Mick, I can not claim to 100% sure but I believe that when Oracle goes
> > to insert a row into a block it checks to see if the block will have
> > less than pctfree free space remaining after the insert. If so, the
> > block is removed from the free list at that time, and the rdbms looks
> > to see if the row will fit in the next block on the free list. There
> > may be some variation to this when long/LOB columns are involved.
> >
> > -- Mark D Powell --
>
> Does this imply that if I insert an unusually large row I could effectively
> obliterate the free list leading to a large amount of wasted space?

I believe that after so many attempts that Oracle graps a free block from above the HWM. That is Oracle will only read so many blocks from the free list to find room; once the rdbms has tried x times and the row has not been inserted then the rdbms gets an unused block moving the HWM. So you should not exaust the free list but yes unusually long rows in a table of normally shorter rows can have a disruptive influence on space utilization.

• Mark D Powell --