Re: How to check the memory usage at a point in time, for unix system?

From: Joel Garry <joel-garry_at_home.com>
Date: 5 Aug 2003 15:43:30 -0700
Message-ID: <91884734.0308051443.7f5d8e43@posting.google.com>

jeffyee_at_hotmail.com (Jeffrey Yee) wrote in message news:<ec4cec95.0308040216.7022e36a_at_posting.google.com>...
> Hi,
>
> I have a RP5470 server, with 2G of memory, 4 CPUs, running on HP-UX
> B.11.11 (11i) os. I have intention to follow the rule of thumb of
> allocating 55% of the memory for the only Oracle instance.
>
> Unfortunately, after allocating 210M of memory to SGA (SGA_MAX_SIZE),
> the PerfView (HP resource & performance management product) says that
> the GLB_MEM_UTIL (% of physical memory in use) is 100%. I don't quite
> believe what I see. Is there a way that I can confirm this, by running
> some UNIX command? I'm looking for information similar to windows 2000
> Server Task Manager/Performance tab, giving the total memory usage and
> the total physical memory.

try

swapinfo -a
dmesg|grep Phys

There really isn't a direct relation with windows memory usage, unix shares more stuff and allows more sophisticated administration. swapinfo isn't likely to agree with dmesg as the admin can allocate memory to the OS - see kernel help description of unlockable memory, and hp.com for descriptions of swap. It is possible to allocate too much memory to the kernel, and be swapping when you shouldn't. If SGA gets swapped, you have big problems. Swap needs to be allocated on disk, but not necessarily used.

IME, that is kind of small physical memory, as well as small SGA. How many users do you have doing what operations?

# swapinfo -a

             Kb      Kb      Kb   PCT  START/      Kb
TYPE      AVAIL    USED    FREE  USED   LIMIT RESERVE  PRI  NAME
dev     4194304       0 4194304    0%       0       -    1 
/dev/vg00/lvol2
dev     1228800       0 1228800    0%       0       -    1 
/dev/vg99/lvol01
reserve       - 2599480 -2599480

memory 6504892 4206896 2297996 65%
[ now I go start up a 3-tier thin client ] # swapinfo -a

             Kb      Kb      Kb   PCT  START/      Kb
TYPE      AVAIL    USED    FREE  USED   LIMIT RESERVE  PRI  NAME
dev     4194304       0 4194304    0%       0       -    1 
/dev/vg00/lvol2
dev     1228800       0 1228800    0%       0       -    1 
/dev/vg99/lvol01
reserve       - 2610380 -2610380

memory 6504892 4207128 2297764 65%

So you can see each time I start up a session for my particular app I use up about 4207128-4206986=142 new Kbytes. But if I look at ps -efl, I see I'm using 11,835 pages. But most of that is shared or something. So the numbers are kind of meaningless until you start swapping, then they are more meaningless. Glance or your perfview might tell you more, but I don't have those at the moment. So this PCT USED is about as useful as anything. This machine has 8G physical, 2 instances with 500 and 860M SGA's, respectively, generally running around 150 sessions of OLTP and ocassional batch. Only complaints stem from poorly designed apps, of course.

>
> Please please help, as my database buffer cache hit ratio is only
> about 30%. Thank you in advance.

Depending on what you are doing, that may or may not be bad, although I suspect it is if you are posting. Which docs are you using to decide?

Also, check out the docs about what rounding SGA_MAX_SIZE does. What does SHOW SGA say?

--
@home.com is bogus.
We're sorry but there was a problem trying to access the requested
page in MetaLink.

Received on Tue Aug 05 2003 - 17:43:30 CDT