Re: Uncommitted Data

On Wed, 15 Jun 2005 07:59:17 -0700, agarwalp interested us by writing:

> Now if the uncommitted record is in the datafiles and information about
> the updated record is present in the redo log. And a checkpoint is
> done. If the database crashes now and then we restart the database
> again, then will old data will be restored by the before image of the
> record in the redo log. or the updated record will be saved.

Not complete description, but should help you with understanding:

That which is committed is in the tablespace data files. It is not 'replayed' for a routine instance recovery.

That which was in transition (a transaction) will be replayed, in part to to recreate the rollback/undo segments so that a clean transaction rollback can occur.

You may also want to review the Oracle Concepts Guide, Chapter 8, which has a decent discussion of each of the processes and describes this in a lot more detail. Esp. look at the 'lgwr' description.

-- 
Hans Forbrich                           
Canada-wide Oracle training and consulting
mailto: Fuzzy.GreyBeard_at_gmail.com   
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