Pythian Video: Oracle RAC VIP’s — Troubleshooting Connectivity Issues

Posted in: Technical Track

Welcome back to our videocasts — this is the last video in the series about Oracle RAC Virtual IP’s. I strongly suggest to watch the two previous videos:

1 — Pythian Video: Oracle RAC — VIP Configuration Mistakes
2 — Pythian Video: Oracle RAC — Why VIPs?

I’m writing this post sitting in Vancouver airport but I won’t get into details of my travel complications here, I think it deserves a separate post as it makes a good point for DR plans. :)

What we are looking at during this videocast is how to troubleshoot the connectivity issues that can be caused by VIP’s in Oracle RAC environment and how to diagnose cryptic Oracle error messages using SQL*Net tracing facility on the client side.

We first look at the typical error message “ORA-12545: Connect failed because target host or object does not exist” and how it leads to the IP alias resolution problem that, at first, seems to be easily fixed by changing IP aliases in the connection descriptor to the numerical IP addresses. Then we find out that it’s not enough with Oracle RAC and server-side connection load balancing can still cause you some grief.

Next, we use SQL*Net client tracing facility and find out where the IP alias resolution happens for addresses in case of connections redirected by a listener to a remote instance — it’s on the client side! Finally, we see how to fix intermittent ORA-12545 errors and understand why Oracle keeps insisting on adding VIP aliases in your DNS and also find out the reliable method of avoiding IP aliases resolution all together by changing server-side listener configuration to use numeric IP addresses instead of VIP aliases.

Well, that was the summary so enjoy the video itself. You probably want to go to Youtube directly to view it in HD – embedded size is not ideal.

As usual all comments are welcome.

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About the Author

What does it take to be chief technology officer at a company of technology experts? Experience. Imagination. Passion. Alex Gorbachev has all three. He’s played a key role in taking the company global, having set up Pythian’s Asia Pacific operations. Today, the CTO office is an incubator of new services and technologies – a mini-startup inside Pythian. Most recently, Alex built a Big Data Engineering services team and established a Data Science practice. Highly sought after for his deep expertise and interest in emerging trends, Alex routinely speaks at industry events as a member of the OakTable.

6 Comments. Leave new

Hi Alex,

Video says it is private and I can’t see it in you list on youtube.

Reply
Surachart Opun
July 27, 2009 3:18 pm

Thank you, I can see it ;)

Reply
Alex Gorbachev
July 27, 2009 2:33 pm

Sorry – I missed to set it to public. Fixed now!

Reply

Great Alex,Keep up the good work…

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Blogroll Report 24/07/2009 – 31/07/2009 « Coskan’s Approach to Oracle
July 31, 2009 9:53 pm

[…] Alex Gorbachev – Pythian Video: Oracle RAC VIP’s — Troubleshooting Connectivity Issues […]

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“also find out the reliable method of avoiding IP aliases resolution all together by changing server-side listener configuration to use numeric IP addresses instead of VIP aliases.”

I tried to use IP instead of DNS short name in the listener.ora and reloaded the listener. LSNRCTL SERVICES command still showing remote listener using DNS short names. So this did not work for me.

Other than listener.ora, what else should I change?

Thanks,
Yibin

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