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oracle architecture
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Message Score Author Date
Hi experts, Need some clarifications on the sce...... akshay rai Apr 18, 2017, 07:22
Rollforward applies only on blocks that have an ...... Score: 700 PtsScore: 700 PtsScore: 700 PtsScore: 700 PtsScore: 700 Pts Michel Cadot Apr 18, 2017, 07:39
Thanks a lot:)... akshay rai Apr 18, 2017, 08:06

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Subject: oracle architecture
Author: akshay rai, India
Date: Apr 18, 2017, 07:22, 182 days ago
Message: Hi experts,

Need some clarifications on the scenario given below,

Consider a scenario where a committed data is being written to the data blocks by the DBwr. Lets say at this point the instance crashes. Now as a part of instance recovery, all the entries in the online redo logs will be rolled forward and all the uncommitted data will be rolled back.

During rollforward, Since some of the committed data was already written to the data blocks by the DBWr, Shouldn't the database through some error like unique constraints or something.( I know it doesnt and rollforward does happen smoothly) . All i wanna know is how exactly it is done.

thanks in advance




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Subject: Re: oracle architecture
Author: Michel Cadot, France
Date: Apr 18, 2017, 07:39, 182 days ago
Score:   Score: 700 PtsScore: 700 PtsScore: 700 PtsScore: 700 PtsScore: 700 Pts
Message:
Rollforward applies only on blocks that have an SCN lower than the SCN in the redo record currently applied.
So if during rollforward Oracle encounters for a data file block with an SCN greater or equal to the SCN in the redo record it just skips it as it knows the job is already done.

Regards
Michel
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Subject: Re: oracle architecture
Author: akshay rai, India
Date: Apr 18, 2017, 08:06, 182 days ago
Message: Thanks a lot:)
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