Purpose of SCAN IP

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Purpose of SCAN IP

Postby sivakumarocp » Thu Jul 25, 2013 4:52 am

Hi Tim,

While I was attending Interview ,the interviewer asked me the purpose of SCAN IP in RAC and I told him all the info given in the below address

http://www.oracle.com/technetwork/produ ... 129069.pdf

after that he just asked me, Only for this purpose does the SCAN concept is introduced!!! I dont' know what to say to the Interviewer at that time.

Please tell me if any feature is there on SCAN other then the info given in that PDF.
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Re: Purpose of SCAN IP

Postby Tim... » Thu Jul 25, 2013 6:39 am

Hi.

The main purpose is that before the SCAN was introduced you had to connect using a TNS entry that listed every VIP in the RAC, so if you add or remove nodes, the TNS entry had to change. That's a pain in the ass, especially for dynamic environments. SCAN allows your TNS entry to contain a single address, no matter how big or small your RAC environment. It is a much simpler solution from a client configuration perspective.

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Re: Purpose of SCAN IP

Postby sivakumarocp » Thu Jul 25, 2013 7:34 am

Hi Tim,

Exactly, I told the same to interviewer, inaddition to that i said like SACN also does Load balancing after that, he asked me like this.

"So only for tns entry and load balancing purpose does the SACN introduced?" he asked me like this

Thats why i wanted to check with you is there any other feature available on SCAN.
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Sivakumar.A
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Re: Purpose of SCAN IP

Postby Tim... » Thu Jul 25, 2013 7:40 am

Hi.

The SCAN doesn't do anything new compared to the previous RAC setup. The old RAC setup did load balancing also. The point it, it simplifies things.

I don't believe RAC does anything mysterious apart from this. Maybe the interviewer was mistaken and thought it had some other value. Maybe they were pressing you to see what your reaction would be. You can tell a lot about a person by the way they react to such things. I'm always honest and would say something like, "If it has any other value, I don't know what it is. What do you think is does apart from what I've said?" :)

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