Re: Backup Oracle ? Online Redo Log.

In article <3c3ebb06$0$24007$4d4eb98e_at_read.news.fr.uu.net>, "Christian M." <cm_at_sdv.fr> wrote:
>Thanks, I made two test of recovery from crash !!!!
>
>The first test is without online redo logs :
>
>1) Restore of my hot backup of the night ( DATAFILES )
>2) Restore of the archived logs of the day since 10:00 am
>
>3) Create blank redo logs files corresponding to the files I have lost.
>If not I have an error with the CREATE CONTROLFILE.
>4) Create crontrol files with command CREATE CONTROFILE with option
>RESETLOGS
>5) RECOVER DATABASE UNTIL CANCEL USING BACKUP CONTROLFILE
>6) ALTER DATABASE OPEN RESETLOGS
>
>It works but I have lost the last transactions stored in the online redo
>logs since 10h00am.

Your examples imply that a complete crash occurs immediately after the hot backup, taking out all files utterly. If that happens, restoring the backed up online redo log might recover completely if it was the last file backed up before the crash (otherwise, it's worthless). However, the possibility that this scenario will happen is probably extremely remote, and could easily be made moot by switching logfiles before and after the hot backup. It's much more likely that a crash will occur well after the "current" online log (at the time of backup) has been archived off. Should that happen, and the existing current log is mistakenly overwritten, you've lost data as well. Since DBA's (juniors and seniors) are human, I'd think it much more likely that whoever's doing the recovery will make that mistake at some point. Seems to me that it's safer not to backup the current logfile (taking the precaution to switch logfiles), than risk the latter, more likely scenario.

JMHO Received on Fri Jan 11 2002 - 08:01:55 CST