topic Re: max_dbc_pct in Operating System - HP-UX

max_dbc_pct

navin — Tue, 23 Sep 2008 17:37:32 GMT

Hello All,
Can some one please let me know lil more info about max_dbc_pct
Thanks much in advance

Re: max_dbc_pct

Tim Nelson — Tue, 23 Sep 2008 17:42:28 GMT

sets the filesystem buffer cache to a percent of total ram.

by default it is 50%. This is way too much and is a BAD default.

for a database system tune to around 2%-3% ( around 500-800mb )

you will also need to modify min_dbc_pct suggest 1% ( or around 100mb)

% obviously depends on how much ram you have.

Re: max_dbc_pct

James R. Ferguson — Tue, 23 Sep 2008 17:49:17 GMT

Hi Navin:

This kernel paramter is used (though 11.23) to govern the upper limit size of the Unix buffer cache:

http://docs.hp.com/en/B3921-60631/dbc_max_pct.5.html

The 'syncer' daemon runs every 30-seconds to flush modified buffers to disk from this cache.

On 11.31 and later, this parameter is replaced by the 'filecache_max' parameter:

http://docs.hp.com/en/B2355-60130/filecache_max.5.html

Regards!

...JRF...