Re: DB_BLOCK_BUFFERS --> DB_CACHE_SIZE

"Howard J. Rogers" <hjr_at_dizwell.com> wrote in message news:40342623$0$15135$afc38c87_at_news.optusnet.com.au...
>
> "Charles Davis" <cdavis10717_at_comcast.net> wrote in message
> news:87-dnd-4qp3muandRVn-gg_at_comcast.com...
>
> Just be warned: if you use the multiple buffer pools feature available
since
> 8.0, then it works completely differently in 9i compared to 8.0 and 8i. In
> 8.0 and 8i, you allocated a total buffer cache (block_buffers x
block_size),
> and then carved bits off that total to give you your other two pools. So
> with block_buffers set to 20000 (ie, 160M), and buffer_pool_keep set to
4000
> (32M) and buffer_pool_recycle set to 6000 (48M), your total buffer cache
> was.... 160M. The two pools come *out* of the total allocated with
> block_buffers.
>
> In 9i, by contrast, db_cache_size only sets the size of the default pool.
If
> you then set db_keep_cache_size and db_recycle_cache_size, those extra
> caches are actually added on: your total buffer cache size becomes the sum
> of all three parameters.
>

Hi Howard,

Just wait a God-damned minute !!

In his tuning book and in various articles, your mate Don Burleson ;) states that if you have a db_cache_size = 3G, a db_keep_cache_size=1G and a db_recycle_cache_size = 500M, then the "Default" pool is 1.5G in size. He states that the Default Pool size = db_cache_size - db_keep_cache_size - db_recycle_cache_size.

Now DB as we know is one of the worlds leading Oracle "experts", surely he can't have this elementary tuning concept incorrect, can he ? I mean, he's only recently published an e-book (at DBAzine) stating exactly what I said above, how can someone tune a database when they don't know how to calculate the size of the Default Pool ???

Yes, I did tell him of this mistake sometime ago and yes he never acknowledged my correction ...

Cheers

Richard Received on Thu Feb 19 2004 - 06:14:37 CST