Log files

[default]

Hi,

Question with Hotbackup.

What is the procedure for backing up logfiles during the hotbackup? Does they really need to be backed up?

Thanks

[marist89]

Yes, they need to be backed up. I would backup your oldest until the logswitch before your backup starts.

[JMac]

Are we talking on-line or archived redo here?

[mrvajrala]

I think Archive Redo Logs !

I also heard , backing up the online redo logs can leads to corruption, correct me if i am wrong ,JEFF >>>

[marist89]

Originally posted by mrvajrala
I also heard , backing up the online redo logs can leads to corruption, correct me if i am wrong

Lead to corruption? I don't see that.

However, backing up online redo logs during a hot backup is pointless. Some even argue that backing up online redo logs during a cold backup is pointless (although I believe the contrary).

[ronnie]

Originally posted by marist89

Originally posted by mrvajrala
I also heard , backing up the online redo logs can leads to corruption, correct me if i am wrong

Lead to corruption? I don't see that.

However, backing up online redo logs during a hot backup is pointless. Some even argue that backing up online redo logs during a cold backup is pointless (although I believe the contrary).

and whats the basis of their belief ?

[marist89]

The theory is that since the database was shutdown normal/immediate anyway no media recovery will be needed when the database comes back up. The redo logs can then be re-created if the database needs to be restored.

However, I am of the opinion that with a cold backup I should be able to get the database back exactly as it was when I shut it down.

See http://www.dbasupport.com/forums/sho...threadid=23565 for this discussion.

[default]

Hi,

I was referring to online logfiles, not the archive logfiles.

Sorry if that cuased any confusion

Thanks

[marist89]

Originally posted by marist89
Yes, they need to be backed up. I would backup your oldest until the logswitch before your backup starts.

[clio_usa]

default,

Here is what I am recommending you to do:

1. Perform a forced checkpoint and a log switch just before backing up the archive redo log files and backup the database files before the archive log files.

2. Backup the control file before the forced log switch/checkpoint, if you lose your online redo logs you will always have to do an incomplete recovery but the intention is that you will not lose much.

3. Have your logs and archived logs on different physical disks/arrays or you risk losing both the logs and the archives in a single disk/controller/cache failure. Be wary of shared caches on disk arrays and whether they are write back or write through.


A backup of the online redo logs is worthless, they do not contain the current data only the data at the time of backup. You do NOT need them to perform a recovery if you have performed a full backup.

Hope that helps,



--clio_usa
OCP 8, 8i, 9i - Senior Oracle DBA
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