Re: anyway to flush the db_buffer_cache?

Sybrand Bakker <gooiditweg_at_nospam.demon.nl> wrote in message news:<k718bv8lpaj0d8b0i6hp272pp8t1jtosfa_at_4ax.com>...
> 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

or alter tablespace xxx offline;

   alter tablespace xxx online;
or alter database datafile xxx offline;

   alter database datafile xxx online;

I think this works in 8i. It should work in 9i as well but I have not tested it.

>
>
> Sybrand Bakker, Senior Oracle DBA
>
> To reply remove -verwijderdit from my e-mail address
Received on Sat May 03 2003 - 17:51:30 CDT