Re: How to apply archive logs on an cold backup

Hi Howard,

Perhaps you can enlighten me a bit in this:

Assumptions are:

Database is in ARCHIVELOG mode
Something catastrophic has happened and all data files, redo logs and control files are lost
All you have is a cold backup taken two days ago You have all archive logs from the cold backup point to the current time
You have a backup of the control file to trace

1. If you restore the cold backup, am I right in thinking that if you issue a RECOVER DATABASE... command, Oracle will reply with a "No recovery needed" (might not be exactly the right wording) message? Presumably this is because the SCN in the data file headers and control file are consistent?
2. In the same scenario as above, assuming you have archive logs available from the time of the cold backup up to "now", how would you roll that cold backup forward? It was in this case that I thought you had to use a RECOVER .... USING BACKUP CONTROLFILE, after creating a new control file from a script?
3. If, as you said in another post in this thread, the CREATE CONTROLFILE script takes SCNs from the data files and writes them to the control file, why, in this scenario is that any different from the situation in 1)? Surely everything is consistent again?

Apologies if I'm ignorant.

Regards,

Tim Kearsley

"Howard J. Rogers" <hjr_at_dizwell.com> wrote in message news:<4135a3eb$0$1501$afc38c87_at_news.optusnet.com.au>...
> Tim Kearsley wrote:
>
> > Depending on what was behind the OP question, I'm not sure that Bob
> > was writing "complete nonsense".
> >
> > A few "ifs":
> >
> > 1) If you have a database in ARCHIVELOG mode and
> > 2) If all you have available is an old, cold backup and
> > 3) If you have all archive logs available since your old, cold backup
> > and
> > 4) If you have a control file creation script (e.g. the output of a
> > BACKUP CONTROLFILE TO TRACE)
> >
> > then you can recover your database back to the current point in time
> > by issuing a RECOVER DATABASE USING BACKUP CONTROLFILE... can't you?
>
>
> Just define what you mean by 'recover you database back to the current
> point'. It is irrelevant for the purposes of assessing that question
> whether your backup is cold or not. The question is: what sort of failure
> have you suffered.
>
> I don't know why that particular message doesn't seem to be getting through.
>
> *IF* you have lost ALL your control files, then a 'using backup controlfile'
> recovery MIGHT be called for.
>
> In fact, your point (4) above means that even now, with all control files
> lost, I would simply be able to execute the backup trace script. Which, if
> you care to read it, you will note does NOT mention 'using backup
> controlfile' syntax.
>
> ONLY if (1) you are in archivelog mode and (2) you have a backup
> (temperature irrelevant) and (3) you lose EVERY copy of your control file
> and (4) you only have a *binary* backup of the control file
>
> ...only *then* do you issue the command 'recover database using backup
> controlfile'.
>
> > A lot of "ifs" I know, but the principle is sound I believe, and I
> > have done it myself on one occasion.
>
> There are no ifs in all of this. There are different recovery scenarios. To
> which the appropriate recovery command response is not a matter of
> guesswork, voodoo or Mystic Meg hypothesising.
>
> Given the list of 4 conditions you specified, you DID NOT need to issue a
> 'using backup controlfile' recovery command.
>
> Period.
> HJR
>
>
> >
> > Regards,
> >
> > Tim Kearsley
> > HBS
> > Milton Keynes Council
Received on Wed Sep 01 2004 - 13:36:51 CDT