topic Re: Clear the cache memory in Operating System - HP-UX

Clear the cache memory

Mousa55 — Sun, 03 Feb 2008 05:58:52 GMT

Hi All,
i Want to know how to clear the RAM Cache memory in HP-UX withot reboot the server
Note: i have rp8420 unix server dividing to 4 partition, ad 11i O.S version

thanks

Thanks & Regards

Re: Clear the cache memory

Zeev Schultz — Sun, 03 Feb 2008 11:12:22 GMT

Lets clarify first what is "RAM cache memory".
Buffer cache?

Basically,you can't delete deliberately contents of system memory - it will cause OS to panic.
So I beleive that you mean something else than system memory or buffer cache memory?

Re: Clear the cache memory

Mousa55 — Sun, 03 Feb 2008 11:25:50 GMT

Hi
yes i want to know how to clear countent of buffer cache memory becuse some application in oracle needed it to this

thanks

Re: Clear the cache memory

Dennis Handly — Wed, 27 Nov 2024 11:04:11 GMT

>I want to know how to clear the RAM Cache memory in HP-UX without reboot the server

You can't. You must reboot to change the kernel parms: dbc_max_pct dbc_min_pct
You can of course let the kernel adjust the memory usage until the next time your reboot.

Here are some threads:
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1177682~~
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1169524~~
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1146263~~
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1120231~~
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1095627~~
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1081391~~
~~http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1059252~~

[Moderator edit: The above links are no longer valid.]

Re: Clear the cache memory

Ivan Ferreira — Wed, 27 Nov 2024 11:07:37 GMT

Maybe you are talking about shared memory. In that case, the ipcrm command can you.

~~http://schogini.us/wordpress/index.php/2005/11/01/oracle-linux-management/~~

BTW, I see in your profile "I have assigned points to 81 of 304 responses to my questions."

Please keep asigning points to the answers that you get.

Have a nice day.

[Moderator edit: The above link is no longer valid.]

Re: Clear the cache memory

Zeev Schultz — Wed, 27 Nov 2024 11:06:29 GMT

Buffer cache as was said is not online tunable.
Strongly suggest to read "buffer cache tuning" part of this doc:

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

I'd say try manually setting dbc_max|min_pct as it fits best your application.

[Moderator edit: Removed the broken link. Please refer to https://support.hpe.com/]

Re: Clear the cache memory

Matti_Kurkela — Mon, 04 Feb 2008 08:32:48 GMT

Maybe the command "sync" is what you're looking for? (see "man 1m sync")

Note that there should be a process named "syncer" running, unless you've disabled it: it runs the "sync" operation automatically in every 30 seconds.

MK

Re: Clear the cache memory

Emil Velez — Mon, 04 Feb 2008 13:11:06 GMT

buffer cache entries get cleared out when you unmount a filesystem. Buffer cache always contains the most recent blocks that were filesystem accessed.

I think what you are discussing is shared memory. IF you are dealing with a 64 bit version of oracle that should not be a problem as long as shmmax is set correctly.

Re: Clear the cache memory

Dennis Handly — Mon, 04 Feb 2008 13:35:59 GMT

>Emil: I think what you are discussing is shared memory. IF you are dealing with a 64 bit version of oracle that should not be a problem as long as shmmax is set correctly.

My assumption is that the Oracle documentation mentions shmmax and also says to reduce dbc_max_pct & dbc_min_pct.