Memory Behavior in HP-UX 11.23

[Brahnda Eleazar]

Peace all,

I'm just curious about a certain behavior in HP-UX 11.23 running Oracle App Server and Oracle Database (10g R2 latest patch).

Our DBA said that in HP-UX, let me just quote him: "I know whenever memory eaten by OS buffer cache, they will never release back, if there still free memory (remember VM memory = Physical memory + swap memory)."

I just want to know whether it is valid from all of your experience dealing with HP-UX. And if it is valid, which tunable parameter that I can work with to avoid this in the future?

Many thanks in advance,
=adley=

[Wouter Jagers · Accepted solution]

Hiya,

The kernel tunables dbc_min_pct and dbc_max_pct denote the minimum and maximum percentage of your physical memory assigned to the dynamic buffer cache.

dbc_max_pct defaults at 50, which, in my experience, is usually way too much. Depending on how much RAM you have, you could try lowering the max value between 10 and 20. If performance remains good, a lot less memory will be 'eaten' by the buffer cache.

Cheers,
Wout

[Venkatesh BL]

Yes, you need to take care of set those above-mentioned parameters correctly. The VM subsystem will start taking off the BC pages only if the limit is crossed.

[Avinash Agarkar]

Hi,

Also the swap should be double from you physical memory you can add more swap also if your oracle apps consuming more physical memory.

set the proper piority of the swap memory.

Thanks,
Avinash

[Brahnda Eleazar]

Peace all,

Thanks guys for the response.
I'll pass the info to the DBA team as well and see what we'll get.

=adley=