Re: Ynt: Creation of Oracle databases

"TurkBear" <noone_at_nowhere.com> wrote in message news:vcemjt40qadrhjkpre3qqsc9bv3b8c3nqg_at_4ax.com...
>
> Not to quibble, but no-- a database does not exist if the power is
 off..data files and executables are there ( altho
> inaccessible until the power is on) but this is not a database...

The text-book definition of an Oracle database is 'Controlfiles plus datafiles plus online redo logs', and therefore without power, the database does still it exist. It only ceases to exist when you formatthe hard disk, or have a head crash rendering the disk unreadable.

> Random words do not make a book, they need to be organized..
> data files and programs do not make a database, they need to be organized
 ( and managed) - the instance does this...
>

The Instance does not organise the database. It is already highly organised, on disk. Datafiles are internally organised with Oracle blocks, for example. All an Instance does is to allow access to that organised information by users. There's nothing to stop you doing a hex dump of a datafile, and retrieving all your data... it wouldn't be pretty, but it could be done.

> My additional 2c to this almost metaphysical discussion...
>

It's not really metaphysical. This is just understanding the basic distinction between an Instance and a Database. One's virtual, one's physical, and there is practically nothing to tie the two together (in other words, if you use the wrong init.ora, when Oracle_SID is set in a particular way, you can very easily end up with an Instance called SALES managing a Database called PURCHASE, with all the SGA settings being those you would ordinarily expect the ORDERS Instance to use).

Regards
HJR
>
> Paul Drake <paled_at_home.com> wrote:
>
> >"Howard J. Rogers" wrote:
> >> Switch the power off, and away they go.
> >
> >excellent use of boolean logic. That sums it up perfectly.
> >
> >power off - database exists - shared memory realm does not exist.
> >
> >bravo.
> >
> >Paul
>
>
>
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Received on Thu Jun 28 2001 - 18:16:49 CDT