Re: Configuring a client TNS entry for TAF
- From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 25 Sep 2018 22:36:10 -0400
Hi!
Replies are in-line
On 09/25/2018 03:10 PM, Will Beldman wrote:
Thank you,
I have a poor understanding of Oracle Services and maybe TAF is the wrong term
so sorry for the confusion. Perhaps what I'm trying to achieve can't actually
be done.
To clarify my configuration, the primary is only a two node cluster and all
clients connect to either node through the SCAN address equally. The standby
is also a two node cluster.
1. I can gently take my database instances in and out of the cluster such that
clients are mostly unaffected (shutdown transactional).
No, you can't. If you take one of your instances down, the clients
connected to that instance will experience an error. They may reconnect,
but they will experience an error.
2. I can do a switchover back and forth from the primary to the standby and
vice versa.
Yes you can. DG broker has made that process very, very easy.
3. I'm trying to add a switchover to a secondary site *such that clients
continue to be unaffected* (or at least as minimal as possible).
You can create a special service and switch it using a startup trigger,
like described here:
https://www.realdbamagic.com/data-guard-client-settings/
However, I am unclear why would you do that? If the purpose is a DR
test, then you should assume that you will lose the whole primary data
center. A manager in a company that has survived the hurricane Sandy has
said that his data center is sleeping with the fishes. Unfortunately,
that was not a joke, although it was a clear reference to the movie "The
Godfather" and therefore very funny. What happened next is that the DR
site was activated and resumed processing, with the total downtime
being 10 minutes. You will need spare application servers, spare DNS
server(s), spare web servers, spare routers, spare firewalls and
standby databases. Spare application servers will have DNS pointing to
the DR TNS entries. My point is that using the primary application
server, redirected to the standby database does not constitute a valid
DR test and tells you nothing about whether your company can survive
something like a hurricane, which is ultimately the goal of any DR test.
Unfortunately today, the only way I can achieve this is to fudge the name
through a DNS update (I have to involve the NOC) or to instruct the use
rs to
update their TNS entries and restart. Both are VERY disruptive!
Why are you switching database roles? Don't switch roles and there will
be no disruption.
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
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