Re: DB block buffers and Shared Pool Size on Oracle 7.3 Windows NT 4.0

In article <909742367.18183.0.nnrp-11.c2ded24f_at_news.demon.co.uk>,   "Dean Cunningham" <drcunningham_at_bewiseltd.demon.co.uk> wrote:
> I am currently running Oracle 7.3 on a dedicated AlphaServer 4100 with 1.5GB
> of memory.
> This machine has only one instance and the physical database is around 30 GB
> with over 60 users and large batch runs.
> The DB block size was set to 4k and the number of block buffers is set to
> 24000 resulting in a cache size of around 90 Mbytes.
> The shared pool size is set to 250 Mbytes. When using NT to monitor the free
> memory at the operating system level it reports that around 1.1 GB is free
> which you would expect. The data dictionary caches are still 100% full and
> there are still misses.

If the dictionary cache hit ratio is over 95% (of course, there are still misses), the performance is already very good.

>There is still over 140 Mbytes of free memory in the
> SGA area so why is this database trying to conserve memory when the
> dictionary cache needs more memory. Is there something in oracle that will
> not allow
> the dictonary caches to use say more than 10% of the SGA.
>
> We have been told by the suppliers of the oracle database that we shouldn't
> change the number of buffers or the shared pool size as they are considered
> massive already considering the size of the database.
>
> Ideally I would like to change the number of block buffers to 80,000 and the
> shared pool size to at least 512 Mbytes to at least use some more memory and
> hopefully achieve a bit more perfromance.

Increasing the db_block_buffers won't help your case. But increasing the shared_pool_size will. In our case, we had buffer cache hit ratio greater than 99%. We reduced the size of buffer cache and increased the size of shared pool.

> Is there some internal limits in oracle or N.T. that would damage the
> database if these changes were made.
>

 No.

> I have heard of some companies running oracle on Windows N.T. with 4 GB
> memory. Surely they cannot be having the same problems and only using 300
> Mbytes.
>
> Any feedback on the above would be greatly appreciated.

We are running three instances and Oracle Financials on an NT box (a Compaq) with two CPUs and 520MB physical memory, over 20 concurrent users. The performance is pretty good.

Xuening Sun

-----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own Received on Fri Oct 30 1998 - 09:12:17 CST