System memory question.

[Leif Halvarsson_2]

Hi,

I installed an Oracle server, rx2660, HP-UX 11.23, Oracle 10.2.

When tuning the kernel I used the recommendations from Oracle. The parameters that was changed is:

shmmax 8589934592
semmns 8192
semmni 4096
ncsize 34816
vps_ceiling 64
shmmni 512
semmnu 4092
ninode 34816
msgtql 4096
msgseg 32767
msgmni 4096
maxuprc 3687
maxssiz_64bit 1073741824
maxssiz 134217728
max_thread_proc 1024
nstrpty 60
scsi_max_qdepth 32
msgmap msgtql+2
dbc_max_pct 10
st_san_safe 1


Now it seems to me as some of these settings is not very realistic. For example, "ninode" is only relevant if using HFS filesystems. And for some of the other parameters, usage is only a few percent.

The Sys memory usage on this server is 1.9GB which seems much to me. I want to free up some memory by decreasing parameters. Which of the parameters above has most impact on the kernel size ?

[Stanimir]

Hi,

For my opinion the changing of Kernel parameters /and K-size at all/ will not impact so much at memory usage. The parameters are OK.
When I do Oracle10.2-instalation, I usually
take the same parameters, "shmmax=available mem".
How much memory you have on this system? May be you could use another way to decrease mem-usage?

Regards,Stan

[Ninad_1]

Hi Leif,

Yes, I agree with the above comments. These parameters are more of a limit than actual usage, except for the dbc_max_pct - which will reserve space from memory for filesystem buffer. It may affect the size of the kernel, but am not too sure how drastically - I believe it should be fine.
The memory usage would actually depend on the parameters defined in the database - buffer, cache etc which will make the PGA (Program Global Area) and SGA (System Global Area). Also depending on the number of connections (client connections) that are connected to the database and what they are doing. And also for 10g, it asks for more memory than if you caompare to 9i or 8i.

Hope this is of some help.
Regards,
Ninad

[Steve Lewis · Accepted solution]

Leif,
I couldn't agree more.

Semmni is way too high, just use ipcs to see how many you are using. When combined with semmns, semmnu and semume the kernel memory grows unnecessarily.

http://docs.hp.com/en/7779/commonMisconfig.pdf

Same for shmmni and shmmns. These don't need to be so high.

Its probably the same for the msg parameters.

The ninode is a very common one. Set it to 5000 or 6000.

These parameters have missed off vx_ninode which means you have the default of 0 - unlimited. Thats the one you need to tune to reduce kernel memory. Set it to the ninode value that you have been given.

The other memory hog is dbc_max_pct, but you have tuned that already and I trust your judgement between DB and OS buffers because you are a salad head.

[Steven E. Protter]

Shalom,

Yes ninode seem irralvent but its a good idea for some mysterious reason to set it and vx_ninode to 90% of it. You can leave it at zero or default but you might run into troubleon that.

You can get some memory back by setting dbc_max_pct lower, but Bill Hassell once related to me that on file based oracle databases there was performance benefit from the buffer cache. This applied to 11.23 not earlier OS releases.

Don't forget to exceed Oracle minimums or Oracle will get quite cranky.

SEP

[Leif Halvarsson_2]

Hi,

Very interesting document. I changed back the ninode, sem- and msg- parameters to default and set vx_ninode to 20000, static cache.

The sys memory went down from 1.9GB to 950MB !


I have not yet seen any negative impact, the number of active vx_ninodes is 1200-1500.