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Online Redo - Different Destination [message #590205]

Mon, 15 July 2013 15:29

Sham.Afrith
Messages: 11
Registered: May 2013
Location: India

Junior Member

hi ,

As you known i am new to oracle. I would like to know that process of redo logs by LGWR.

i already have 3 redo log groups and their status are

SQL > select group#, status from v$log;

GROUP# STATUS
------ ------
1 INACTIVE
2 INACTIVE
3 CURRENT

i added new log group as 4 to new destination path. the new path is different disk (external Hard disk ). Because of production as policy followed "Multiplexing redo".

SQL > ALTER DATABASE add logfile group 4
('h:\orcl\redobackup\redo04a.log', 'h:\orcl\redobackup\redo04b.log')
size 100m;

after altered the database i got another group and that status follows

GROUP# STATUS
------ ------
1 INACTIVE
2 INACTIVE
3 CURRENT
4 UNUSED

now my doubt is exactly this. All the tiny transactions by the database is written to online redo. but my new redo log file group is still UNUSED, that meant that is ready to use. if i lost my first 3 redo online files then how i will get recover from the 4 redo group ?

thanks is advance

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Re: Online Redo - Different Destination [message #590210 is a reply to message #590205]

Mon, 15 July 2013 16:38

John Watson
Messages: 8984
Registered: January 2010
Location: Global Village

Senior Member

You have misunderstood the concept of "multiplexing". It means that different members of the same group should be on different devices, so if you lose one device the other member will still be available.

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Re: Online Redo - Different Destination [message #590226 is a reply to message #590205]

Tue, 16 July 2013 00:10

Michel Cadot
Messages: 68765
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

All these kinds of question are answered in Database Concepts.

Regards
Michel

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