backup question

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Originally posted by jmodic
The most recent backup is the cold backup from last night and DBA knows exactly what he has to do with cold backup. After all, everybody knows that - simply restore everything from the tape and that's it. After restore is complete, he begins recover database to apply archlogs. And after all archlogs are applied - bummer! He realised that he has overwritten online redo logs with the ones from cold backup! So he has to open database with resetlogs anyway, but more importantly - he lost all the transactions from online redo logs! He has lost them forever, unrecoverable, because redo logs were overwritten by unusable ones from cold backup.
[Edited by jmodic on 10-04-2002 at 02:03 PM]

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Yeah, that was a pretty stupid thing to do, but I can see it happening. I can buy your argument.

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Originally posted by np70
AFAIK Once you open database with RESETLOGS, all your previous backups are invalid because SCN gets reset.

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No, they are not "invalid" as such. I mean I wouldn't get read of all my old backups once I had to open the database with resetlogs.

Those backups are still perfectly valid and usable if you want to perform point-in-time recovery to any time prior to your resetlogs. They are only not usable for recovery operations that require you to perform recovery to any time past resetlogs. And that is why you need to perform full backup ASAP after you open the database with resetlogs.

"Export/import is not a backup methodology..."
- Yoda



Firday afternoon humor :)

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Originally posted by np70
AFAIK Once you open database with RESETLOGS, all your previous backups are invalid because SCN gets reset. Thats why Oracle recommends to take cold backup after RESETLOGS.

please let me know if i missed something..

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it's log sequence that gets reset not SCN

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Originally posted by gopi
"Export/import is not a backup methodology..."
- Yoda



Firday afternoon humor :)

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Hey, hey, hey. I'm all for the YodaMeister, but I believe that was my homework for DscoBob... http://www.dbasupport.com/forums/sho...6&pagenumber=3

Back up of redo log files are used only when we go for cloning. Cloning is done only to produce replica of production data base, for testing purpose.
I dont think we use backup set of redo logs to recover any production database (we apply archive logs intead). If you consider the amount risk (oooof, you have replaced the the present redo log file with back up redo log files) involved in taking backup of redologs files and the amount of data you lose (while cloning to produce test database) if you dont take back up of the redo files, we can avoid taking back up of redo log files.

It's risk of replacing the production logfiles with older ones versus losing small amount of data in test databases.

Again, it all depends on persons.. (Sanjay and Modi)

Quote:

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Originally posted by jmodic
After restore is complete, he begins recover database to apply archlogs. And after all archlogs are applied - bummer! He realised that he has overwritten online redo logs with the ones from cold backup!

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jmodic, I agree about the risk you mentioned.

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Originally posted by pando
please refer Note:61801.1 on Metalink

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Thanks for the link, pando. That clears my doubt about RMAN restore from coldbackup.

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Originally posted by nagarjuna
It's risk of replacing the production logfiles with older ones versus losing small amount of data in test databases.

Again, it all depends on persons.. (Sanjay and Modi)

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BTW, there is no risk of losing any data (even if you don't backup redo logs) provided you shutdown your database normal or immediate before backup.
I was only arguing about the need of RESETLOGS if you don't backup redo logs.

Sanjay

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Originally posted by SANJAY_G

Quote:

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Originally posted by nagarjuna
It's risk of replacing the production logfiles with older ones versus losing small amount of data in test databases.

Again, it all depends on persons.. (Sanjay and Modi)

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BTW, there is no risk of losing any data (even if you don't backup redo logs) provided you shutdown your database normal or immediate before backup.
I was only arguing about the need of RESETLOGS if you don't backup redo logs.

Sanjay


[/B]

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We dont apply archive logs when we refresh testdatabase. Instead we just restore all the database files. Inthis case, we lose small amount of data if we dont have backup of logs files ;)

And we all good DBAs I guess and we know that it's mandatory to give RESETLOGS when we set our log sequence to zero. :)

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Originally posted by nagarjuna
We dont apply archive logs when we refresh testdatabase. Instead we just restore all the database files. Inthis case, we lose small amount of data if we dont have backup of logs files

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You do not lose any data (not even small) if you had shutdown the database in NORMAL or IMMEDIATE mode before cold backup.
The datafiles are checkpointed when you do a NORMAL or IMMEDIATE shutdown and all trnasactions in redo logfiles are already written to datafiles.
You just need to do RESETLOGS to recreate the redo log files if you have lost them. :)

Sanjay

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Originally posted by SANJAY_G

You do not lose any data (not even small) if you had shutdown the database in NORMAL or IMMEDIATE mode before cold backup.
The datafiles are checkpointed when you do a NORMAL or IMMEDIATE shutdown and all trnasactions in redo logfiles are already written to datafiles.
You just need to do RESETLOGS to recreate the redo log files if you have lost them. :)

Sanjay

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Oppps I missed out the check point thing during database shutdfown.. I dont learn from my mistakes :) I missed out the same question in my OCP exam. and missing it in work place too.. It looks like I am not a good DBA ;)