topic Re: Problem with memory in Operating System - HP-UX

Problem with memory

alymarcor — Mon, 14 Mar 2005 12:39:35 GMT

Hello everybody,

I have a problem with some data from memory. I don't understand why if I have 4GB memory installed when I see monitor performance tool I only see 2GB of real memory. Can somebody explain me what happen with memory and what is the meaning of memory active, virtual memory active, etc? Aditional in the event log of Oracle application appears the following message: HPUX Error: 233: No buffer space available. I atached a document with print screen of problem and Oracle log. Please help me,

Thanks,
Alymarcor

Re: Problem with memory

Kent Ostby — Mon, 14 Mar 2005 12:56:14 GMT

Here are some definitions

Real Memory: Amount of real memory in the machine thatis available to user processes and the virtual paging system
(not held by the kernel)

Active: Real memory currently being used.
Total: Total real memory in the system.

Virtual Memory:
Amount of virtual memory (also called pseudo-swap) in the system (as defined by pstat (see pstat(2)):
Active: Virtual memory currently in use.
Total: Total virtual memory in the system.

Re: Problem with memory

RAC_1 — Mon, 14 Mar 2005 12:59:38 GMT

Do you have glance installed? Then post following glance -m

You may have default buffer cache set-i.e
dbc_max_pct at 50%.

kmtune -lq dbc_max_pct
kmtune -lq dbc_min_pct
kmtune -lq nbuf
kmtune -lq bufpages

No Buffer space available error can be caused by number of reasons.
Post following

swapinfo -mta
glance -m
ndd -get /dev/tcp tcp_conn_request_max

Anil

Re: Problem with memory

alymarcor — Mon, 14 Mar 2005 13:21:06 GMT

I don't have glance installed. I want to somebody tell me if the server is utilized the total of 4GB of memory or only 2GB.

Re: Problem with memory

John Payne_2 — Mon, 14 Mar 2005 13:41:03 GMT

Alymarcor,

If you have Online diagnostics installed, you can go look for yourself.

for cstm:

cstm
map
sel dev nn [where nn is the device number for memory]
info
il

The information log will tell you what slots you have memory in, the sizes, total amount of memory, status, any errors, etc.

There is also an X related command, xstm. Select memory, run infomation. The report will come up.

Hope it helps

John

Re: Problem with memory

A. Clay Stephenson — Mon, 14 Mar 2005 14:11:00 GMT

You are being confused by the output of 'top'. Top is a meaningless tool for analyzing memory usage because you are reading something into it that is not there. Top only knows about memory related to processes; it reports nothing about kernel data structures such as buffer cache.

Re: Problem with memory

Sathish C — Tue, 15 Mar 2005 01:56:02 GMT

Hi
try using ipcs -mobt to see how may shared segments have also been occupied by other processes .

Re: Problem with memory

Isralyn Manalac_1 — Tue, 15 Mar 2005 02:16:12 GMT

Another way to look how much physical memory you have is to check it in /var/adm/syslog/syslog.log. Search for "Physical".

Regards,

Isralyn

Re: Problem with memory

alymarcor — Tue, 15 Mar 2005 10:12:09 GMT

Thanks for your comments... But I don't understand why if I have 4GB of memory installed in the server, it uses 3.5GB of swap and only 2GB of memory active. You can see that in the document I have attached...

Thanks,
Alymarcor

Re: Problem with memory

Steve Steel — Tue, 15 Mar 2005 10:18:59 GMT

Hi

To be sure look at

ftp://eh:spear9@hprc.external.hp.com/memory.htm

It is a good site with great memory tools

Steve Steel

Re: Problem with memory

Steve Steel — Tue, 15 Mar 2005 10:25:46 GMT

Hi

This is probably an oracle issue with
memory leaks

#define ENOBUFS 233 /* No buffer space available */

What ENOBUFS means:
===================
In many cases, ENOBUFS just means there's no sufficient memory available and the system(kernel) can not allocate more

Steve Steel

Re: Problem with memory

Ted Buis — Fri, 18 Mar 2005 17:57:28 GMT

I'm with RAC. You likely have the maximum buffer cache set in the kernel at 50%. Typically this is too much. Also, you if you are using Oracle DB, then unless you have OnlineJFS you are double buffering and really making poor use of RAM. See the attached performance cookbook.