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hot backup [message #308365] Mon, 24 March 2008 02:35 Go to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
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hi Experts,
some days before i went for an intervier asked me the question that when we put database in backup mode why lots of redo get generated i said because during backup mode datafile header get freezed this may be the reason. he does not seems satisfied with my answer.
so could any body explain me the same?

Thanks,
Sheldon
Re: hot backup [message #308372 is a reply to message #308365] Mon, 24 March 2008 02:54 Go to previous messageGo to next message
Michel Cadot
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1/ Don't rate your question
2/ Post in the correct place: backup interview question must in either "homework, certification, training" forum or "backup" forum

Point 1 prevent me from answering, too bad, you tried to get attention in an unfair way, you have no answer from me.

Regards
Michel
Re: hot backup [message #308376 is a reply to message #308372] Mon, 24 March 2008 03:01 Go to previous messageGo to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
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ok
was not knowing i thought its an interview so i must give it a rate so everybody can voew it and learn otherwise you can see i have never given rate to any of my question.

Re: hot backup [message #308378 is a reply to message #308365] Mon, 24 March 2008 03:12 Go to previous messageGo to next message
varu123
Messages: 754
Registered: October 2007
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When datafile is in backup mode,oracle copies the first modified block to the redo log files.
When the same block is modified again ,only the modified part is copied.

Since DML continues as normal,lots of redo blocks are copied to the redo files and hence lots of redo is generated.

Re: hot backup [message #308379 is a reply to message #308376] Mon, 24 March 2008 03:13 Go to previous messageGo to next message
Michel Cadot
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There are more redo logs generated because the first time a block is modified after "begin backup" it is fully written in the redo logs and not just the modifications as in the normal process.

Regards
Michel
Re: hot backup [message #308382 is a reply to message #308379] Mon, 24 March 2008 03:15 Go to previous messageGo to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
Member
i told him the same answer he told me
why lots of redo get generated.
Re: hot backup [message #308383 is a reply to message #308365] Mon, 24 March 2008 03:18 Go to previous messageGo to next message
varu123
Messages: 754
Registered: October 2007
Senior Member
Quote:
i told him the same answer he told me
why lots of redo get generated.



Then you should have told him again.
BTW, the answer is not so simple as it looks.
Re: hot backup [message #308386 is a reply to message #308383] Mon, 24 March 2008 03:25 Go to previous messageGo to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
Member
i told him that when we take the tablespace in backup mode
datafile header get freezed and scn number stops updating
this may be the reason he does not seem satisfied after this reply.
Re: hot backup [message #308398 is a reply to message #308386] Mon, 24 March 2008 03:50 Go to previous messageGo to next message
Michel Cadot
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And this is not the same thing as I wrote.
You didn't explain why there are more redo generation with what you posted.

Regards
Michel
Re: hot backup [message #308400 is a reply to message #308398] Mon, 24 March 2008 03:54 Go to previous messageGo to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
Member
my fisrt reply was the same which you posted but when he asked me again then my reply was the one which i wrote now.
so i think i was right.

Re: hot backup [message #308404 is a reply to message #308400] Mon, 24 March 2008 04:01 Go to previous messageGo to next message
Michel Cadot
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So you should ask him if there was anything wrong with your answer that would let you the opportunity to complete or precise it.

Regards
Michel
Re: hot backup [message #308406 is a reply to message #308404] Mon, 24 March 2008 04:04 Go to previous messageGo to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
Member
the thing is that i did not get selected
let it be now i am confident that my answer was correct.

Thanks
Re: hot backup [message #308407 is a reply to message #308365] Mon, 24 March 2008 04:07 Go to previous messageGo to next message
varu123
Messages: 754
Registered: October 2007
Senior Member
Post other questions also.
They might be useful to others.
Re: hot backup [message #308408 is a reply to message #308407] Mon, 24 March 2008 04:09 Go to previous messageGo to next message
sheldon1982
Messages: 59
Registered: February 2008
Location: india
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yea sure i will
Re: hot backup [message #308411 is a reply to message #308407] Mon, 24 March 2008 04:20 Go to previous messageGo to next message
Frank
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Registered: March 2000
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varu123 wrote on Mon, 24 March 2008 10:07
Post other questions also.
They might be useful to others.

How would other users benefit from that?
So they can learn the answers to these questions, in order to pose themselves as more experienced or expert than they really are?
Re: hot backup [message #308418 is a reply to message #308365] Mon, 24 March 2008 04:46 Go to previous message
varu123
Messages: 754
Registered: October 2007
Senior Member
Quote:
So they can learn the answers to these questions, in order to pose themselves as more experienced or expert than they really are?



Just by mugging up some inaccurate answers.
I don't think so.

I take it as a reason to look in to the docs.
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