Re: DB Buffer Cache Size

"Niall Litchfield" <niall.litchfield_at_dial.pipex.com> wrote in message news:<4127b7c9$0$20250$cc9e4d1f_at_news-text.dial.pipex.com>...
> "Howard J. Rogers" <hjr_at_dizwell.com> wrote in message
> news:412753cb$0$25143$afc38c87_at_news.optusnet.com.au...
>
> > Maybe when you have 100GB of RAM to throw at your caches (and a disk
> > subsystem to match) you can afford it. Most people can't.
>
> Arguable I'd say, given the overhead that this would generate. I'm not at
> all sure that allocating that RAM to PGA might not be more appropriate for
> most apps that deal with stupidly large datasets
>
> > > db_cache_size = 4000M
> > > db_recycle_cache_size = 500M
> > > db_8k_cache_size = 200M
> > > db_16k_cache_size = 4056M
> > > db_2k_cache_size = 35430M
>
> The sum of the above is 44186M or 43.1G. I'm almost sure that this is 1.1gb
> too much.

Let us say I have tuned PGA_AGGREGATE_TARGET and I still have RAM available.
I would think increasing DB_CACHE_SIZE related parameters will help improve
the performance of selects because physical disk i/o is reduced. I thought reason Oracle
provides 64 bit version, so one can take advantage of large memory by having large SGA's. People talk of main memory database where entire database can be
placed in memory. The only way I know of doing that in Oracle is to do caching using db_cache_size related parameters.

If I have an OLTP application where I do many inserts, deletes, updates in addition to selects, do you think performance of my inserts, deletes, updates will be reduced because of large db_cache_size. Received on Sat Aug 21 2004 - 22:16:59 CDT