| Recovery [message #175613] |
Sat, 03 June 2006 05:53  |
gajini
Messages: 262
Registered: January 2006
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Senior Member |
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Consider the follwing scenario,
A commit checkpoint say ChkPt1,Which updates the datafile,redo log file & control file header with
the current SCN.Suppose if any recovery is required,it'll happen upto this SCN value.
After some point of time,another Checkpoint(say ChkPt2) is issued manually,now all the uncommited
data is written to the files in the disk & updates the datafile,redo log file & control file header
with the current SCN.
Suppose if now recovery is required,
1) Will oracle recover to SCN recorded at ChkPt1 or to SCN recorded at ChkPt2?
2) If it've to recover to SCN recorded at ChkPt1,where it'll get that info,since
datafile,redo log & control file headers are updated with the SCN value occurred
at ChkPt2?
3) In this scenario,what will be the role of rollback segment,how & what info it provides
required for this scenario?
I'm very much confused by this scenario/doubt for a long time,please anyone clear it.
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| Re: Recovery [message #176062 is a reply to message #175613] |
Tue, 06 June 2006 13:18  |
smartin
Messages: 1803
Registered: March 2005
Location: Jacksonville, Florida
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Senior Member |
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In this case, I would agree that you really need to spend some time reading about oracle backup and recovery. Oracle has excellent documentation about it, the backup and recovery concepts and guides. You need to understand the concepts first before you start understanding specific scenarios.
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| Re: Recovery [message #176076 is a reply to message #175613] |
Tue, 06 June 2006 18:07 |
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BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal
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Senior Member |
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From my perspective COMMIT <==> new SCN.
After a OS/Oracle crash (unclean termination), Oracle will "recover" to the highest/most recent SCN.
In other words it will present data as though the highest SCN was just COMMITed after starting database.
Media recovery is a totally different situation.
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