RAC nodes regularly freezes for about 10 seconds

From: Marcin Szarek <me_at_some.where.com>
Date: Fri, 18 Aug 2006 12:21:06 +0200
Message-ID: <pan.2006.08.18.10.21.05.717573@some.where.com>

Hi!

For a few months we suffer mysterious problem with Oracle 10g RAC (more details on server configuration at the bottom). At regular basis (every 5 minutes) nodes of our cluster "freeze" - during couple of seconds operating system for some mysterious reason does nothing - as far as we're concerned - in userspace. Every single userspace process stops for this period. After a few seconds system comes back to life and all suspended processes content for CPU time and other resources, which in effect leads to higher load.

We tried many investigations, which brougt us to following conclusions:
- when Oracle instance is stopped, freezes disappear

• since the moment we reduced shared_servers parameter from 60 to 20 freezes last unsignificantly shorter (about 4 seconds shorter)
• after instance restart freezes are unnoticeable, but as times goes by, they are again as long as 6-9 seconds

Unfortunately investigation is very hard. /var/log/messages reports nothing, dmesg reports nothing, Oracle alert log also has nothing to say.

Have you any idea what may be misconfigured or damaged? Could you please suggest us some further tests?

Thank you in advance for any followups!

Database server characteristics

---

OS: RHEL 3 ES
Kernel: 2.4.21-32.ELsmp
Oracle: 10.2.0.1.0
Storage: SAN accessed by QLogic HBA
Cluster storage: OCFS v.1

-- 


-        MARCIN SZAREK <me_at_some.where.com>           -

-- There are only 10 types of people in this world; --
-- those who understand binary, and those who don't --

Received on Fri Aug 18 2006 - 05:21:06 CDT