Re: why does db_block_buffers always show 0

From: Richard Foote <richard.foote_at_bigpond.com>
Date: Tue, 19 Aug 2003 13:52:31 GMT
Message-ID: <zYp0b.46098$bo1.24527@news-server.bigpond.net.au>

"Mark D Powell" <Mark.Powell_at_eds.com> wrote in message news:2687bb95.0308190534.39846c39_at_posting.google.com...
> quarkman <quarkman_at_myrealbox.com> wrote in message
news:<oprt4c4ktezkogxn_at_haydn>...
> > On Mon, 18 Aug 2003 22:07:47 +0200, Sybrand Bakker
> > <gooiditweg_at_sybrandb.demon.nl> wrote:
> >
> > > On Mon, 18 Aug 2003 19:28:11 GMT, "Anurag Varma"
> > > <avarmadba.skipthis_at_yahoo.com> wrote:
> > >
> > >> And: if you just set db_block_buffers, then it should come into
effect
> > >> (Have
> > >> not tried it,
> > >> but documentation seems to state that).
> > >
> > >
> > > It does, but you will be basically running 8i memory management, so
> > > you can't change your SGA dynamically.
> > >
> > >
> > > Sybrand Bakker, Senior Oracle DBA
> > >
> > > To reply remove -verwijderdit from my e-mail address
> > >
> >
> >
> > There'll also be a dirty great warning flashed at you immediately you
issue
> > the startup command reminding you that you are using deprecated
parameters.
> > It will still open, but the warning is a bit disconcerting, to say the
> > least.
> >
> > Interesting that you say "you can't change your SGA dynamically",
because
> > it's actually still true in 9i that you can't change your SGA
dynamically,
> > either. Oh, you can certainly *re-distribute* memory between the various
> > caches on-the-fly, but the total amount of SGA is utterly fixed at
whatever
> > SGA_MAX_SIZE is set to (or computed to be if it's not explicitly set),
and
> > SGA_MAX_SIZE itself cannot be modified dynamically. A cunning piece of
> > Oracle marketing, I think, calling the ability to alter the size of a
few
> > caches 'dynamic SGA'.
> >
> > By the way: to Daniel... Undo tablespaces do not have to be of the
> > db_block_size size, but can be of any of the non-standard sizes. TEMP
> > however, must be db_block_size (as must SYSTEM, as you said).
> >
> > Regards
> > HJR

>

> Question HJR, is there any recommendation for selecting the blocksize
> of temp based on the other block sizes in use? Personally, I think we
> plan to keep one size for all unless we start using LOBs, but we are
> open to the concept. I am not sure I want the hassle of tuning
> multiple pools. I had to manage multiple pools back in my IMS days,
> and DB2 supports multiple block sizes, but I suspect that most DBAs
> would be better off using one block size and letting Oracle manage the
> pool on its own.

>

Hi Mark,

You have no choice, the block size of a temporary tablespace must be the default size.

And as Howard has said in the past, the default block size should be based on the file system buffer size. If using raw, then generally a larger block size is best. With only very few and rare exceptions, multi block sizes provides flexibility with transportable tablespaces, it's not a database tuning feature per se.

Cheers

Richard Received on Tue Aug 19 2003 - 08:52:31 CDT