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Newbie questions abt data guard [message #474499] Mon, 06 September 2010 14:59 Go to next message
ultgnp
Messages: 105
Registered: May 2010
Location: Germany
Senior Member
Hi,

I have a Database of Size approx 150GB. I want to create a standby server(High Availability). I have few questions,which some experts here can help me with.

Scenario

1)If our Primary Database crash, the standy server should instantly start automatically i.e no down time.

2)There should be no data loss.

3)Are Data Guard and Replication similar?


Thanks,




[Updated on: Mon, 06 September 2010 15:05]

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Re: Newbie questions abt data guard [message #474506 is a reply to message #474499] Mon, 06 September 2010 15:12 Go to previous messageGo to next message
Michel Cadot
Messages: 59991
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
1) No.
2) Depends on your configuration, this is an option you took when you configured your data guard.
3) No, although standby database may be one way to replicate.

Regards
Michel
Re: Newbie questions abt data guard [message #474510 is a reply to message #474506] Mon, 06 September 2010 15:40 Go to previous messageGo to next message
ultgnp
Messages: 105
Registered: May 2010
Location: Germany
Senior Member
Thanks very much MIchel for such a quick reply. Could you please suggest some solution for less down time i.e point no 1.

Thanks,
Re: Newbie questions abt data guard [message #474539 is a reply to message #474510] Tue, 07 September 2010 00:41 Go to previous messageGo to next message
Michel Cadot
Messages: 59991
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
RAC, disk array replication, and if you stay to data guard standby database, fast network, powerful machine (the standby must be as powerful as the primary one).
See http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/rac_support.htm#i636474
You have to choose between downtime and data loss.

Regards
Michel
Re: Newbie questions abt data guard [message #474642 is a reply to message #474539] Tue, 07 September 2010 16:00 Go to previous message
John Watson
Messages: 4859
Registered: January 2010
Location: Global Village
Senior Member
In reply to your question 1, you can get very fast automatic failover with Data Guard. The default delay for the fast start failure initiated by the Data Guard Broker Observer is 30 seconds. Of course there is a bit more time needed to activate the standby.
The delay is more likely to be making sure that your clients connect to the new primary immediately the original primary fails. You need a startup trigger that detects the mode in which the database is operating, and starts the appropriate service for registration with the listeners. Something like this:
CREATE TRIGGER ROLE_REGISTRATION AFTER STARTUP ON DATABASE
DECLARE
        ROLE VARCHAR(30);
        OPENMODE VARCHAR(30);
BEGIN
        SELECT DATABASE_ROLE INTO ROLE FROM V$DATABASE;
        SELECT OPEN_MODE INTO OPENMODE FROM V$DATABASE;
        IF ROLE = 'PRIMARY' THEN
                DBMS_SERVICE.START_SERVICE ('PROD');
        ELSIF ROLE = 'PHYSICAL STANDBY' THEN
                DBMS_SERVICE.START_SERVICE ('STANDBY');
        END IF;
END;
/

Then, if you have appropriate settings in your tnsnames files, your clients should reconnect their broken sessions automatically to the new primary.
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