Re: Improper Load Balancing

Donald

It may not be relevant in your environment, but we had similar problems in a three tier system (OC4J webserver, OC4J app server, RAC database, 9iR2). The problem was that all app server nodes had the same configuration - so they all tended to connect their first N sessions (the session pool minimum) to the same node. You could be seeing the same thing; web clients are nicely load balanced, but the web-to-DB connection isn't. When the session pool is created, there's no load on the RDBMS - so a connection storm (like server startup) tends to hit one node - load metrics are only updated slowly (after a few seconds at least) - so SQL*Net load balancing just isn't suitable (at least at 9iR2 RAC) for session pools; you have to help it along.

More background on what we did to work around this and a related problem (if you are interested) here: http://preferisco.blogspot.com/2006/04/micro-partitioning-pooled-sessions-in.html

Regards Nigel

• Original Message ---- From: "Freeman, Donald" <dofreeman_at_state.pa.us> To: oracle-l_at_freelists.org Sent: Thursday, March 22, 2007 12:55:16 PM Subject: Improper Load Balancing

We are experiencing problems with the database connectivity from the production web servers for the last 2-3 weeks. We are using Oracle RAC in the production and there are 2 database servers. Somehow the connection goes to one database server intermittently, not all the time. But when it happens we see most of the connections going to the same Oracle node i.e. second node. We are using Windows load balancing on the web servers. Does anybody have any idea what might cause this? Don Freeman
Database Administrator 1
Bureau of Information Technology
Pennsylvania Department of Health
(717) 703-5782

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