Memory & swap space

[Dennis Handly]

>#swapinfo -tam
memory 16363 4488 11875 27%
total 32747 13782 18965 42%

I don't see that 99% memory usage? Was that during the peak?

[KINGSLEY_1]

dear Sirs,

I see the 99% when i use glance.

Thanks

[Hein van den Heuvel · Accepted solution]

> Physical memory: 16GB
> instance: 1
> instance size: 126GB
> sga Maxsize: 6GB
> SGA Target: 4GB

Ok, 6GB SGA for 16 GB system feels alright. So that's not directly the image.

We'll have to figure out where the rest of the memory went. With dbc_max_pct @50, it could be sitting in the buffer cache to the tune of 8GB, ready to help or or give back under pressure. With 11.31 the giving back works well. With 11.23 it is my understanding that it is less effecient, and thus you may want to reduce dbc_max_pct to say 10%.


#ipcs -m

Ooops, I should have asked ipcs -ma or -mb
That will give a size column


Anyway, I'm not yet convinced there even is a problem. So the memory is in high use, with low free. Great! The system is using the memory that was bought for it. Excellent.

What is the problem?
Performance issues? How do you tell? Tell us.
Instability (why is that due to low memory)?
Is there a high PI or PO rate during regular work?

Regards,
Hein

[KINGSLEY_1]

Dear Sirs,

Our banking application hangs during peak hours. And the memory ultilisation rises to 99% when monitered with glance.

If i may ask , can i reduce " dbc_max_pct 50 Default Immed" to let us sy 15 or 20? And what will be the implication on the banking application and also the oracle database?

Thank you.

Kingsley

[James R. Ferguson]

Hi (again):

If i may ask , can i reduce " dbc_max_pct 50 Default Immed" to let us sy 15 or 20? And what will be the implication on the banking application and also the oracle database?

I think that would be a good move to make. Since Oracle has its own buffer cache, caching more of the same in the UNIX buffer cache is wasteful. You could monitor read-hit ratios with 'sar -b' before and after adjusting the 'dbc_max_pct' if you like. Empirical measurements will tell you the implication of your change in *your* environment.

Regards!

...JRF...

[Hein van den Heuvel]

>> Our banking application hangs during peak hours.


define 'hang'! We all have our own understanding/expectation for that.

I suspect that here it means that all end user applications became unresponsive.

But what it the system doing at that time besides using memory?

Why do you thing high memory use is relevant at all for the purpose of the hang? Please be specific!

- Is the CPU busy? top?
- Apparently you can use GLANCE.
- What else can you use? df? ls -l for Oracle files? df ?...
- What can you NOT use... (errors, or getting stuck).
- Are all Networks operational (ping, telnet, ftp, ssh, tnsping, remote non-application table oracle access)
- What does Oracle (Enterprise Manager) report when/while it hangs?
- Is Oracle responsive to local SQLplus queries at all? (select * from v$instance)
- Can local Oracle execute some banking query


Just the fact that you only mentioned 'hang' without specifics other then a potentially irrelevant high memory usage suggest to me that you may want to escalate this issue, and get more external and internal help.

You may want to prepare some answers to the questions above to get the best possible help. For now it is not clear whether yo shoudl engage an Oracle, Network, Storage or HPUX expert. Personally I would engage them in the order I list them. yes, that impleis that I think this is least likely to be an HPUX problem, allthough a good HPUX resource may help yo pinpoint the problem.

Good luck
Hein

[KINGSLEY_1]

Dear Sirs,

One more hint. During peak hours, when the banking application slows, syslog.log reads

"Sep 28 16:12:25 t24dbpro inetd[1057]: chargen/tcp: accept: No buffer space available

Sep 28 16:12:25 t24dbpro inetd[1057]: discard/tcp: accept: No buffer space available

Sep 28 16:12:25 t24dbpro inetd[1057]: daytime/tcp: accept: No buffer space available

Sep 28 16:12:25 t24dbpro inetd[1057]: telnet/tcp: accept: No buffer space available

Sep 28 16:12:25 t24dbpro sshd[931]: error: accept: No buffer space available

Sep 28 16:12:25 t24dbpro inetd[1057]: ftp/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: swat/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: dtspc/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: printer/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: auth/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: exec/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: shell/tcp: accept: No buffer space available

Sep 28 16:12:26 t24dbpro inetd[1057]: login/tcp: accept: No buffer space available

Thank you

kingsley

[Hein van den Heuvel]

Hmm,

Does that perhaps also suggest that _some_ (new) end users hang, but others can keep working)?

This may be a TCP configrutation issues such as : tcp_conn_request_max

See for example:
http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=237561

In there Rick Jones (albeit in 2003) wrote
"Indeed, 99 times out of ten, this message has nothing to do with availability of memory. It means that by the time the server application got around to calling accept() on the listen socket, the remote client had given-up (for wahtever reason) and aborted the connection. The exact reason why an ENOBUF is returned in this case in HP-UX 11.X is starting to get lost in the mists of time"

also....

https://forums.sdn.sap.com/thread.jspa?threadID=1477203

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=969702

good luck,
Hein

[KINGSLEY_1]

Dear Sir,


tcp_conn_request_max=4096

Thank you

Kingsley

[chris huys_4]

Hi,

The problem is memory pressure.

Log a case with HP support, get the kmeminfo utility, issue kmeminfo;kmeminfo -user;swapinfo -tam, during a "hang", and this info should give enough indication as to what causes the problem and how to resolve it.

Greetz,
Chris