Re: Recovery practice

Comments embedded

On 15 Apr 2005 12:32:30 -0700, "PHernandez" <phph109_at_yahoo.es> wrote:

>Hello group!
>
>Trying to understand how to recover after some types of disasters.
>
>When I delete all control files, all log files and all database files
>at the same time- I'm fried...
>
>I can't recreate the control file since the data files are missing, and
>I can't restore data files since the db doesn't mount without a control
>file...
>
>The "backup" of the controlfile was taken by using
>SQL> ALTER DATABASE BACKUP CONTROLFILE TO TRACE;
>

which just doesn't contain any information about the current transaction state of the database, especially it doesn't contain the current S(ystem)C(ommit)N(umber).

>If I instead had used
>SQL> ALTER DATABASE BACKUP CONTROLFILE TO '/oracle/backup/control.bkp';
>
>could I have done
>$ cp /oracle/backup/control.bkp
>/u01/app/oracle/oradata/test/control01.ctl
>and been saved?

Yes, exactly. But then how likely is it you loose all copies of your controlfile in a crash?
Rman (when properly configured) autobackups the controlfile in this format.

>
>I need better understand the nature of control files, right?

Look up v$controlfile_section in your database, connected as SYS and you will see exactly which *state information* the controlfile contains.

>
>I'm reading
>Backup and Recovery Basics (B10735-01)
>Backup and Recovery Advanced User's Guide (B10734-01)
>
>The test system is White Box Linux and Oracle 10g in archivelog (using
>the flashback area). This rman script is run weekly:
>
>---
>connect target;
>run {
> RECOVER COPY OF DATABASE WITH TAG "S";
> BACKUP INCREMENTAL LEVEL 1
> FOR RECOVER OF COPY WITH TAG "S"
> DATABASE;
>}

This is a very strange and likely dangerous script as it makes an *incremental* backup (ie changed blocks only). You do have a level 0 backup somewhere don't you? Otherwise you are toast.

>---
>
>And finally, no I'm not a DBA- I'm just a poor sysadm that was told to
>keep an eye on Oracle meanwhile the company finds a new one [DBA]...
>
>
>Thanks,
>ph

--
Sybrand Bakker, Senior Oracle DBA