Re: anyway to flush the db_buffer_cache?

Sybrand Bakker wrote:
>
> On Sat, 03 May 2003 16:56:21 GMT, "Ryan" <rgaffuri_at_cox.net> wrote:
>
> >Im doing some tuning now and its hard to establish benchmarks if all the
> >blocks are in memory. So for tuning purposes only Id like to flush them out
> >to test different methods.
> >
> >Im not a good enough tuner to simply analyze a plan and no for certain what
> >to do.
> >
>
> It doesn't really matter. The amount of logical I/O will remain the
> same whether the blocks are in memory or not. The goal of your tuning
> should be to reduce the logical I/O, not to get the hit ratio up. If
> that's your goal there more than enough tuning books around
> recommending what to do. Try it! just issue set autotrace on explain
> stats and run your query 2 times and see what happens.
> If you really want to flush the buffer cache there are 2 methods
> - run a full table scan on any table bigger than the buffer cache
> - bounce the database
>
> Sybrand Bakker, Senior Oracle DBA
>
> To reply remove -verwijderdit from my e-mail address

A full scan will not necessaily clear the cache because Oracle will do its best not to allow full scans to do so.

Off-then-on-lining a tablespace will clear the buffers.

hth
connor

-- 
=========================
Connor McDonald
http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue"