Finding filecache usage hp-ux 11.31

[Sean M.]

I apologize if this has been addressed in another forum post, but I did not see anything geared towards my question on ITRC or in the 11.31 CSA book.

In HP-UX 11.31 you have a filecache_min and filecache_max parameter.

Currently our system is set to 5%/25% on the parameters (default I think).

kctune -q filecache_min
Tunable Value Expression Changes
filecache_min 3266613862 5% Imm (auto disabled)
kctune -q filecache_max
Tunable Value Expression Changes
filecache_max 16333069310 25% Imm (auto disabled)


Total VM : 40.0gb Sys Mem : 12.6gb User Mem: 22.8gb Phys Mem : 64.0gb
Active VM: 8.1gb Buf Cache: 1mb Free Mem: 13.9gb FileCache: 14.7gb

I want to see about freeing some of this file cache up for another database instance we are installing. How can I identify what percentage or number of i/o requests are actually hitting this cache? I'm trying to find a command to identify per mount point or total.

Thanks

[melvyn burnard · Accepted solution]

you could maybe take a look at the kcuseage command, for example:
kcuseage -ht filecache_max

man kcuseage

[Dennis Handly]

>melvyn: man kcuseage

It would probably help to spell it kcusage. :-)

[Steven E. Protter]

Shalom,

Your idea has merit. On this OS file cache, which is the equivalent of the old buffer cache provides some benefit to the database.

What is hard to quantify is whether allocating the same memory to oracle is more beneficial.

My feeling is that it would be good to drop that filecache_max figure and allocate it to the SGA of an Oracle database.

Also of note: The kernel can be tuned to use a lot less memory. this is a pretty big system, and we managed to cut kernel use at our big Oracle server by 35 percent, just by looking at use and reducing parameters, this one included. **Last contract.

SEP

[melvyn burnard]

Blast the difference between English and American English spelling

[Sean M.]

Thanks for the responses all, the kcusage was what I was looking for (I'm suprised the CSA book did not contain information on it). I ended up tuning it down without any issues in order for our dbas to increase the SGA and db cache settings.

[JC Arzate]

Im triying to confirm is there´s a risk in set this Kernel parametert at low level, I mean HP see some risk?? Do we can just set it down??
Of course according original Note I´ll use this resources for Database Instance.
$ uname -a
HP-UX ebsbdpro B.11.31 U ia64 1659469384 unlimited-user license
$ kcusage -ht filecache_max
Tunable: filecache_max
Setting: 16307607550
Time Usage %
=============================================
Thu 09/16/10 11:15 CDT 15955652608 97.8
Thu 09/16/10 11:20 CDT 15954894848 97.8
Thu 09/16/10 11:25 CDT 15962861568 97.9
Thu 09/16/10 11:30 CDT 15928664064 97.7
Thu 09/16/10 11:35 CDT 15933124608 97.7
Thu 09/16/10 11:40 CDT 15883358208 97.4
Thu 09/16/10 11:45 CDT 15909007360 97.6
Thu 09/16/10 11:50 CDT 15794868224 96.9
Thu 09/16/10 11:55 CDT 15821049856 97.0
Thu 09/16/10 12:00 CDT 15717101568 96.4
Thu 09/16/10 12:05 CDT 15682842624 96.2
Thu 09/16/10 12:10 CDT - -
$

Expect for comments.