| instance recovery.... [message #259591] |
Thu, 16 August 2007 01:13  |
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Hi there,
Probably thats a very much basic question but some how I am much confused somehow in it.
I have read the concept and backup/recovery guide.
My doubts are as follows
(1) How Oracle starts finding the blocks to be recovered at the mount stage?Will it go and scan the entire datafiles of the db to find the blocks which are not consistent?f not than out of the whole datafiles,how it will distuinguish those who needs recovery and are going to get committed data?This doubt is for the roll forward at the mount stage.
(2)In the open stage, there may be a stage when the old data in the undo is already purged/overwritten of one transaction by another.If that will happen than how ORacle will get the old data for that transaction?
thanks in advance and regards,
Aman....
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| Re: instance recovery.... [message #259893 is a reply to message #259677] |
Thu, 16 August 2007 14:43  |
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Hi Michel,
For
(1) How Oracle starts finding the blocks to be recovered at the mount stage?Will it go and scan the entire datafiles of the db to find the blocks which are not consistent?f not than out of the whole datafiles,how it will distuinguish those who needs recovery and are going to get committed data?This doubt is for the roll forward at the mount stage.
You replied
Oracle applies active online redo logs on each file. It knows for each file what was the last checkpoint time (scn) as this is in the header of the file.
My doubt is that will oracle apply the all of online redolog file
s or it will start from only those redo enteries which are ahead form the current Redo Byte Address?
Thanks and best regards,
Aman....
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