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RE: Opinions on B&R scenarios

From: Fink, Dan <Dan.Fink_at_mdx.com>
Date: Wed, 23 Oct 2002 14:09:16 -0800
Message-ID: <F001.004F1CC3.20021023140916@fatcity.com>


Under this scenario, you have 2 options
1) Incomplete recovery to 2:10:30. Since there are no tablespaces in backup mode, this is possible.
2) Do a complete recovery to the point of failure at 2:15:30. Of course, if the failure was manual (oops, I dropped a table in production), then this is not a valid recovery because it would return you to the state immediately following the failure.

Also consider this scenario:
Well after the backup has completed, it is determined that data has been logically corrupted and the database needs to be recovered to the point in time immediately prior to the corruption. If the corruption occurred at 02:15:30, the only option is to perform an incomplete recovery to 02:10:59.

I looked in my notes from the Oracle8 Internals Seminar and this is the explanation. Incomplete recovery is not allowed during a hot backup (while ts was in hot backup mode). Because the high scn is not recorded (in the datafile), the recovery logic does not know how to perform a recovery. The first time when incomplete recovery is possible is at the checkpoint immediately following the end of hot backup mode (which may be delayed in some releases).

Does this make sense?

-----Original Message-----
Sent: Wednesday, October 23, 2002 3:45 PM To: Multiple recipients of list ORACLE-L

Dan,

What you intend to say is that if the database crashed at say 2:15:30, you can do an incomplete recovery upto say 2:10:30, right? Why cant I do a complete recovery ? or what stops me from doing an incomplete recovery until 2:15:25?

Raj

<<snip>>
                                 

02:00 1st tablespace begins backup
02:10 1st tablespace ends backup
02:11 2nd tablespace begins backup
02:21 2nd tablespace ends backup
02:22 3rd tablespace begins backup
02:32 3rd tablespace ends backup

etc.

You could then perform an incomplete recovery until 02:10:01 - 02:10:59 or 02:21:01 - 02:21:59, etc.

<<snip>>

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Author: Fink, Dan
  INET: Dan.Fink_at_mdx.com

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Received on Wed Oct 23 2002 - 17:09:16 CDT

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