This content has been marked as final. Show 40 replies
yxes2013 wrote:Scenario is like THIS:
Hmmm I am confused....So if my database crashed for the day and I have a backup last night, + plus I have redos intact I do not have to worry lost transactions? even if I do not have archived logs?
The scenario is like this:
Archiving turned off.
The system.dbf got removed accidentally or got corrupted.
I need to restore from backups last night and recover the transactions for the day stored in the redos. Is it possible?
I am thinking that all the online redo logs still holds all the transaction for the day.
07:00) Database starts up for the day. All you have is the cold backup taken prior to startup, and you stated you do not want to take archivelogs.
07:30) Database activity fills redo-1, switch to redo-2
08:00) Database activity fills redo-2, switch to redo-3
08:30) Database activity fills redo-3, switch to redo-1
09:00) Database activity fills redo-1, overwriting activity from 7:30 to 8:00, switch to redo-2
09:30) Database activity fills redo-2, overwriting activity from 8:00 to 8:30, switch to redo-3
10:00) Database activity fills redo-3, overwriting activity from 8:30 to 9:00, switch to redo-1
10:30) Database activity fills redo-1, overwriting activity from 9:00 to 9:30, switch to redo-2
11:00) Database activity fills redo-2, overwriting activity from 9:30 to 10:00, switch to redo-3
11:30) Database activity fills redo-3, overwriting activity from 10:00 to 10:30, switch to redo-1
12:00) something bad happens to a data file.
Now, how are you going to recover those transactions from 7:00 to 10:30 ????
Please explain to your company's management that you lost 3 1/2 hours worth of transactions because you didn't want to learn how to use the fundamental backup and recovery tool provided with the database.
Edited by: EdStevens on Feb 15, 2013 6:58 AM
The OP is talking of 10 Redo Log Groups of a large size -- e.g. 1GB.
Assuming that the total redo generation between two cold backups does not exceed 10GB, he should be able to restore and recovery from last night's backup using the online redo logs (without any archives). That also assumes that only datafiles are lost (corrupt) and not online redo logs !
Hemant K Chitale
So are you convinced ed? ;)
I fully understand Hemant's point.
My question to you is, are you willing to bet your company's data on the idea that you will never, ever completely fill all of your redolog groups between backups AND will never, ever lose a complete redo log group? ON that second point, aside from any mis-guided faith you place in your hardware, let me ask two more questions. First, what is the name of your redolog files? Second, what is your SA going to do when he thinks he's running out of disk space, and in looking for candidate files to delete, sees a bunch of files named something.*log*?
yxes2013 wrote:And so is Hemant. He and I are in agreement. We are just pointing different aspects and considerations of the same principle.
Yeah, thats what I meant :)
But I also understand Ed's point and I know he is right ;)
I am just making a scenario where it can be possible to happen for the sake of argument discussions, and not really to recommend it.
Edited by: yxes2013 on 18.2.2013 17:59