Re: Recovery - online redo log issue (ORA-00338)

Tom Robinson wrote:
>
> > I backed up all the files except the online redo logs as recommended
> > by Oracle.
>
> For offline backup, you must include controlfile(s), datafiles and
> online redo logs.

No, backing up online redo logs is never required for any backup.

> I believe the recommendation is for online (hot) backups.

It'd be more correct to say that the recommendation against backing up online redos is for all archivelog mode databases, regardless of whether you're doing hot or cold backups. The danger is twofold: 1) you accidentally restore them after a crash/media failure combo, overwriting transactions in the existing online redos and 2) if you do restore a cold backup including online redos and therefore you don't open resetlogs, you will generate multiple timelines for redo - i.e. you will generate multiple copies of archive logs with the same name and sequence number, again causing confusion (and possibly corruption) in the event of a subsequent recovery.

In my opinion you should never be in the habit of backing up online redo logs, regardless of whether your database is in archivelog mode or not. It doesn't really help you for noarchivelog mode databases, and it can really burn you for archivelog mode databases.

To get back to the original poster's question though, it appears he restored the datafiles and controlfile from the cold backup, but not the online redo logs (which he said he didn't backup). Upon startup, the database sees that the online redos have newer SCN's (i.e. are more current) than even the controlfile. So it sounds like from his description that he needs to clear these logfiles out with a series of 'alter database clear logfile group "x"' statements, one for each group. They don't contain any relevant information, and need to be zeroed out by Oracle to start fresh. This, I suppose, is the only disadvantage to not backing them up as part of a cold backup of a noarchivelog database.

Regards,
Sean Received on Wed Apr 17 2002 - 23:14:54 CDT