Re: LRU algorithm - question

to expand a bit

The original poster was right - blocks from a FTS are cached, but are placed at the LRU end of the list. This often *has the effect* of wiping them out of memory before the end of the FTS, but not always. Moreover if alter table <tablename> cache; has been run against the table (Oracle 7/8.0.x) then any FTS of that table will still result in the blocks being placed at the MRU end of the list. In any event Oracle uses (AFAIK) the same aging algorithms regardless of type of read. The only difference is where on the list the read blocks are placed.

In later versions of Oracle (8i?) tables subject to FTS can be placed in their own private buffer pool (lookup buffer pool keep) Here they are still subject to aging but you can of course size the pool large enough that they never get aged out.

HTH

--
Niall Litchfield
Oracle DBA
Audit Commission UK
"Steve Adams" <steve.adams_at_ixora.com.au> wrote in message
news:39cec750.394909349_at_nsw.nnrp.telstra.net...


> Hi Roger,

>

> That's not right.

>

> @   Regards,

> @   Steve Adams

> @   http://www.ixora.com.au/

> @   http://www.christianity.net.au/

> @

> @   Going to OpenWorld?

> @   Catch the Ixora performance tuning seminar too!

> @   See http://www.ixora.com.au/seminars/ for details.

>

> -----Original Message-----

> From: "Roger" <NOrgSPAM_at_mcs-hh.de>

>

>

> Blocks from a full table scan are not cached.

>

> Regards

>    Roger

>

> <sergey_s_at_my-deja.com> schrieb im Newsbeitrag

> news:8qjp3s$b30$1_at_nnrp1.deja.com...

> > Data blocks placed in cache at the most recently used end "age out" by

> > moving to the least recently used end where they get removed from

> > memory.

> >

> > What happens to the blocks from full table scans? I know they are placed

> > at the least recently used end, but do they remain in cache for some

> > time? Is there also some sort of "aging out" process?

> >

> > Thnk you!

> > Sergey

> >

> >

> > Sent via Deja.com http://www.deja.com/

> > Before you buy.

>

>

>