I'm facing a critical problem in RHEL AS 5.

When i start the server along it uses only 4% of RAM. After than i start oracle and uses 25%-35% of RAM. but after a while it's growing and uses 95%-97% of RAM.

How can i reduce the hish usage of RAM.

BTW, when i shutdwon the oracle database it still hold the 95% of RAM.

Can you please tell me the reason or any solution to overcome the memory management problem.

Is it a problem ???.
Does it affect your service to clients ???.

Bying more RAM is one way, but you didn't specify how much RAM you actually have (so is there any sense in bying more of it, or is it more important to find out if this is a bug or something).

First find out what is actually using all the memory, and for what (buffers or something for example?). Then start thinking if it should use that much RAM or not.. Are you suffering slowdowns because of filling RAM, and how much swap space is used? I mean, is it going so high you're out of memory, or is it just using most of the RAM available?

Here is the query results

1. Free -m command output
total used free shared buffers cached
Mem: 8115 8085 29 0 19 7691
-/+ buffers/cache: 374 7740
Swap: 16386 34 16352

2. top output
top - 16:33:29 up 3 days, 4:21, 3 users, load average: 0.00, 0.00, 0.00
Tasks: 111 total, 1 running, 110 sleeping, 0 stopped, 0 zombie
Cpu(s): 1.8% us, 0.6% sy, 0.0% ni, 90.0% id, 7.6% wa, 0.0% hi, 0.0% si
Mem: 8310532k total, 8282788k used, 27744k free, 20368k buffers
Swap: 16779884k total, 35308k used, 16744576k free, 7875948k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
13497 oracle 15 0 2355m 68m 62m S 2 0.8 0:02.65 oracle
1 root 16 0 2492 548 468 S 0 0.0 0:01.25 init
2 root RT 0 0 0 0 S 0 0.0 0:00.06 migration/0
3 root 34 19 0 0 0 S 0 0.0 0:00.00 ksoftirqd/0
4 root RT 0 0 0 0 S 0 0.0 0:00.06 migration/1
(partial)

3. It affect my services to my client also
4. My physical memory is 8GB and Swap is 16GB
5. I'm suffering slow down because of filling of RAM

From your numbers, I do not think that lack of free memory is your problem here.

The figure you should be looking at is the total of (free + buffers + cached), since otherwise "free" memory is used by Linux to hold onto data as long as possible in order to speed up disk reads and writes (among other things). This shows up under "buffers" or "cache", not "free", so having a low number in the "free" column should not indicate low performance in and of itself.

You have in this example 8115 Mb in total, of which 29Mb is free (meaning utterly unused, wasted memory), 19Mb buffered and 7691Mb cached. This means that you have effectively got 7739Mb free or used only as cache memory, so free memory space isn't your problem here.

One problem could be the amount of data you have in swap. This is data temporarily written out to disk in order to free up memory, and is often a cause of slowness.

You might try looking at the /proc/sys/vm/swappiness file; this controls how much data is swapped out to disk purely to free up memory for caching. This is usually a bad thing if you have very slow hard disks (or very fast RAM and processor compared to your hard disk speed). To turn it off completely, you can run:
as root.

You could also try looking for warning or error messages in /var/log/messages to see if there is anything that could indicate a problem.

Hope that's of some help,

—Robert J Lee

Thanks for your early reply. I've got one problem. But i have some more questions.

1. Can I modify the buffer cache ratio? if yes how?
2.How can I optimize Linux system to faster access of application?
3. Is there any relation of kernel (smp,hugemem etc.).

you have 7691MB cached in your memory ... thats perfect, your kernel uses free memory for buffers and cache ... this memory can be freed if system needs free memory ... look at free result ...

free + buffers/cache = 7740 MB !!!

you have 4.6% memory usage by programs (and kernel)

That's the generally accepted mantra - not always the case.
Sounds like an application design problem - I'd be inclines to try the swappiness suggestion above (immediately after a reboot).

Can i Control Memory buffer or cache in RHEL?

see this for exmple ... more in Google :-)

http://www.novell.com/brainshare/eur...ons/tut303.pdf