Re: backup without archivelog mode

HiYa

In article <a7hb54$9fg$1_at_lust.ihug.co.nz>, some kind human wrote:
>Archivelog mode simply means that you can guarantee recoverability of all
>transactions. If you can guarantee recoverability by some other mechanism,
>then no, you don't need archivelog mode.

perhaps I misunderstood archivelog mode, I thought it was to mean that the data in the redo log was written out by the archiver process, to files, rather than being over written as the redologfiles filled ... maybe I dont quite get when the redolog's are and are not used in the firstplace....

>
>By that, I mean that these nightly loads must be coming from some source.
>If you can back that source up, and are prepared to repeat a nightly load if
>something happens to the database, who cares about archives?!

not me .... that was why I was asking.

> A lot of
>sites, for example, will use SQL Loader to load millions of records from a
>text file. Since the text file can be burnt to CD, or put on tape, the load
>could be repeated if ever there was trouble on the database.

my intention ... but I'd prever to only have to recover and then redo a single load, as it will taketime and this is a reasonably mission critical database.

>
>But: You can never, ever make a copy of any database file whilst the
>database is running, without that copy being internally inconsistent. And
>only archive logs guarantee that you can make an internally inconsistent
>datafile consistent.

damn ... theres that consistent word again, I am going to have to get to what that really means ... is it not the sequence of where Oracle is in all of its threads? Cant I just trash the logfiles, and the control files, and rebuild from a script from the trace file (command syntax escapes me now)??

ok ... so its sounding like we need to use archivelog mode, or cold only.

>So: your choice. If you can repeat the loads, and
>don't mind doing so, don't bother with archives. But then all backups will
>require that you shut your database down before making a backup.

I guess that since its not in use all the time, I could just do nightly cold backups as long as the time taken to copy the files fited into my window of available time ....

>If you want to take hot backups (which your use of the 'alter tablespace
>Florence begin backup' command suggests you want to do) then you will
>absolutely, positively have to be in archivelog mode. There is no exception
>to the rule that hot files cannot simply be copied. It matters not the
>slightest that no-one is doing anything but selects. *Oracle* will be doing
>things that cause the all-important SCNs to increment at unexpected
>intervals -at which point, you wouldn't be able to use the hot-copied files.
>

ahhhh .... so thats why!

>If your database is up when you take backups, regardless of what it's doing,
>it's a hot backup. You must behave as though it were a hot backup. And hot
>backups require archivelog mode.
>

OK ... I was sorta thinking that if nothing happened in that time, that the redologs wouldn't fill, and I'd be able to copy things, and not have any details in the redologs overwritten.

thanks for your help

See Ya

--
(when bandwidth gets better ;-)

Chris Eastwood
Photographer, Programmer, Motorcyclist and dingbat

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