Re: Best Practice
Date: Thu, 19 Jan 2012 12:08:03 +0200
Message-ID: <OFCD3C9470.7827829F-ONC225798A.0034B9CA-C225798A.0037AB8C_at_seb.lt>
We had an interesting case: a network failure between our DC's (data centers - one is used as primary and the other as standby as far as databases are concerned)
Both(!!) standby and primary db's where just fine and running at the moment of failure.
BUT: application servers are distributed between DC's for capacity reasons. Meaning there is no ACTIVE-PASSIVE DC as far as application servers and user request load balancing is concerned. Both DC's are active, both can serve customer requests.
Given those conditions the decisive factor wich DC to prefer depends on
which DC is "more" accesible to the outside world so that customers can
still submit requests to app servers.
That means the observer (BTW, a very correct name - OBSERVER ) must OBSERVE
the databases (BOTH of them) from the same place as your most important
customer.
In our case observer runs on standby DC. It decided to failover of course. The decision happened to be the correct one at least from admins point of view: the failover DC was still accessible to us, we could connect and restart what failed to failover, etc. End users could connect too.
You see: you need to consider what end customer functionality needs HA most and start from that. What's the purpose to have a failover if the DC is not accesible to the end users?
If only isolated db/db server failure is concerned then you can run your observer on just a standby server. It will do the job: primary goes down, observer is running on standby, standby fails ower.
brgds, Laimis N
Please consider the environment before printing this e-mail
From: mek s <sidi.bouzid.meknessy_at_gmail.com>
To: ORACLE-L <oracle-l_at_freelists.org>
Date: 2012.01.19 10:53
Subject: Best Practice
Hello,
We are designing a DR solution using Oracle Data Guard 11gR2.
1- Physical Oracle Data Guard with Primary / Standby database.
2- Use Maximum Availability Mode.
3- Use the Observer for automatic failover.
4- Turn on Flashback databases.
5- Use the broker.
We only have site A and site B. The primary will be placed in the Site A and the standby with be placed in the Site B.
The primary database will run on host 1 in the Site A. The standby will run on the host 2 in the Site B.
The observer will run on the host 3 (Until now, we don't know where to place the observer; in Site A or Site B) but it will run on one of the application host.
Now, Questions;
1- After a fail over / switch over, will the observer point monitor
automatically the standby site or do we need to point the observer manually
to monitor
the new primary site?
2- Giving my configuration (having only 2 sites), What is the best place to
put the observer? What is recommended? I know that the best solution is to
have a third environment
but, in my case we only have 2. what are your suggestions based on your
real world set up?
3- Giving my configuration (having only 2 sites), What is recommended to have a *HA solution for the observe*r , without the use of Grid Control?
Thank you,
S
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Received on Thu Jan 19 2012 - 04:08:03 CST