Re: Is there any harm in setting very large db_cache_size even when buffer hit ration does not increase?

Prem K Mehrotra wrote:
> I have sevel GB's of memory on my HP UNIX server. My buffer hit ration is
> low (50%). I have increased db_cache_size (Oracle9i) gradually. I have not
> seen increase in hit ration all that much. My question, is there any harm
> in increasing db_block_size so it uses 1Gb or more of memory (which is avaiable
> to Oracle database instance) without causing any impact on other applications
> on that sever. Actaully, my server is mainly a database oracle server. There
> are a few application scripts which run in the night for a few minutes.
>
>
> I would think more memory I use by increasing db_cache_size will help the
> performance even if hit ratio is not increasing all that much (i.e.
> it is 55% instead of 95%.
>
> Prem

Ready, Fire, Aim!

Exactly why do you think that increasing BCHR is a "Good Thing" (TM)? You've already demonstrated that increasing the db_cache_size has little to no impact on BCHR. What make you conclude that increasing it more will do more good than harm?

Do you realize that there are scripts which will provide any BCHR you select? Since this is a proven reality, please aceept the reality that the BCHR is a mythical indicator of performance.

Let's speculate...
Assume you can increase BCHR from 50% to 90%, exactly what does that mean WRT response time for your application?

You are fixated on a meaningless number WRT Oracle performance.

Your time would be better spent find slow SQL statements & making them faster. Received on Thu May 20 2004 - 21:04:54 CDT