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Hotbackup [message #239599] Tue, 22 May 2007 13:23 Go to next message
rsreddy28
Messages: 295
Registered: May 2007
Senior Member
Hello All,

I was asked in an interview like


" The Tablespace USERS is being kept in hot backup mode and while copying the datafile to the new location, the developers are doing heavy transactions say almost upto 100 Mb and committed within those few minutes of copying and after copying the datafile to another disk, the tablespace has been out of backup."


Now the question is, will the committed transactions of 100 Mb be in the copied new location or Not.What will happen to those transactions.

Kindly let me know.

Hope the question is clear.

bYe,

Raj
Re: Hotbackup [message #239600 is a reply to message #239599] Tue, 22 May 2007 13:35 Go to previous messageGo to next message
DreamzZ
Messages: 1666
Registered: May 2007
Location: Dreamzland
Senior Member
http://jaffardba.blogspot.com/2007/03/alter-database-begin-backup.html

[Updated on: Tue, 22 May 2007 13:49]

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Re: Hotbackup [message #239606 is a reply to message #239599] Tue, 22 May 2007 13:51 Go to previous messageGo to next message
Michel Cadot
Messages: 64131
Registered: March 2007
Location: Nanterre, France, http://...
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Some are and some are not but who cares?
The important point is that Oracle can recover in case of media failure, for this it uses (archived) redo logs which contains the begin backup and end backup tags.

But now, you should use RMAN and never worry about begin/end backup. This is, I think, the best answer.

Regards
Michel
Re: Hotbackup [message #239609 is a reply to message #239606] Tue, 22 May 2007 13:55 Go to previous messageGo to next message
rsreddy28
Messages: 295
Registered: May 2007
Senior Member
Hi Michael,


Thanks for your reply , but this question was asked in an interview , so can you do me a favor by reading my question and answer me that. I;m very much confused what would be the best answer for that.

Re: Hotbackup [message #239610 is a reply to message #239609] Tue, 22 May 2007 14:18 Go to previous messageGo to next message
Michel Cadot
Messages: 64131
Registered: March 2007
Location: Nanterre, France, http://...
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I answered to your question:
Quote:
Some are and some are not

And sometimes interviewer asks a question but the correct answer is not the direct reply to the question.
I do that just to see if knowledge is just scholar one or real experience.

Regards
Michel
Re: Hotbackup [message #239612 is a reply to message #239599] Tue, 22 May 2007 14:27 Go to previous message
saibal
Messages: 111
Registered: March 2007
Location: India
Senior Member
See, the moment you put the USERS tablespace in backup mode, a checkpoint occurs only for that tablespace and the SCN for that tablespace is locked. Now when you copy the underlying datafile to a new location, that datafile is not ever going to be a consistent backup, because, with the database open, any copy of the datafile can never be guaranteed to be consistent. In fact, more than likely it will be a fuzzy copy, requiring recovery. It absolutely doesn't matter how much or how little work is going on during the period the file was being copied--the file WILL REQUIRE RECOVERY UPON RESTORATION AND THAT IS IT. Now the recovery will happen from the point the SCN was locked--the whole purpose of locking the SCN is to know the earliest point from which to begin recovery. All the heavy activity that you were talking about will flow from the redo logs into the archived logs, and thus you have all the work done and waiting in the archived logs.When you take your tablespace out of backup mode, there will be another checkpoint as it will try to catch up with all the other tablespaces in the database.
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