topic Re: dbc_max_pct in Operating System - HP-UX

dbc_max_pct

Shahul — Mon, 24 Feb 2003 09:50:39 GMT

Hi

I have some boxes with 512MB RAM. Right now dbc_max_pct is set to 50%. This is affecting the perfomeance. I wanted to reduce this, Can some one suggest me the suitable value for better performance?

Thanks in advance
Shahul

Re: dbc_max_pct

Steve Steel — Mon, 24 Feb 2003 09:59:54 GMT

Hi

put it to about 10-20%

or use bufpages to set a fixed amount

Steve Steel

Re: dbc_max_pct

Stefan Farrelly — Mon, 24 Feb 2003 10:06:25 GMT

The maximum size for dbc_max_pct should be 300-350MB so depending on how much ram you have you should do the math and set dbc_mac_pct accordingly. eg. if your server has 3Gb of ram set dbc_max_pct to a max of 10-12 (%).

In your case in may only be affecting performance because you dont have much memory and need to free up some RAM for other applications, in which case simply set it as low as you can manage - eg, 2-3%.

Re: dbc_max_pct

monasingh_1 — Mon, 24 Feb 2003 10:07:44 GMT

In most situations, I will keep it at 8-10% at the most. So that other application get to get some memory...

Also will, depend what are you using the box for, like in oracle, you should compromise buff_cache to sga of oracle, In this situation I will definitely go to only 5%..

If you do lots of filesystem IO then more buff_cache will help, which seems to be not your case anyway,your performance is already slow at 50%.

hope thishelps..

Re: dbc_max_pct

Pete Randall — Mon, 24 Feb 2003 11:28:23 GMT

Shahul,

Without knowing what release you're running and what the boxes are being used for, I would have to say you need more RAM. Tuning dbc is not going to give you a significant benefit. Go out on the used market and pick up another 512MB or so, then you might have enough room to begin worrying about dbc.

Pete

Re: dbc_max_pct

Jose Mosquera — Mon, 24 Feb 2003 12:15:28 GMT

Hi,

The recomendations are from 5% to 10% depends on the total amount of memory in your system. The minimun value must be 300MB, then you can try to put a low percentage. After you do this and reboot your dont want to see the USED line for the device lines from swapinfo -mt > 0. This means no memory pressure and no paging. This will increase performance considerably.

But in your case the total physicall memory (512MB) is really very poor, I recommend you to buy more physical memory.

Rgds,