Re: Oracle instance and database question

Petr Hamza wrote:
>
> Dear all,
>
> This question will probably look simple and selfevident to you. I am newbies
> in Oracle world, I have until now worked only with MS SQL servers, so please
> execuse me.
>
> The question is: Can an Oracle instance have more databases or it may have
> just only one?
>
> In MS SQL you have server process and this process may serviced number of
> database. There is normal practice to create a new database whenever you want
> to separate data. It is perfectly normal to have 5 or more database on one
> server and the hardware requirement are the same as with one database with
> the same number of users. It seems to me that Oracle instance may have only
> one database and creating a new instance increases the hardware requirements
> (2 instances - double the hardware of the first instance). Is this true?
>
> Any help is welcome
>
> Thank you
>
> Ivo Sedlacek
> DCB, Actuaries and Consultants
> sedlace_at_dcb.cz

Hi

Oracle has databases, instances and schemas. In a simple way, a database is a set of datafiles containing the data. a instance is defined by the background processes and the SGA. a database can have one
or more instances (distributed servers) accessing the same datafiles. an instance can have one or more schemas. a schema contains the objects (tables, views,
etc.) which belongs to a user.

If you take a 1:1 relation between database and instance. it's true that the HW req.
"increase" when you add an additional instance (additional memeory used for the SGA).
you might need additional discs (new datafiles). It depends on your server if you need additional HW or if your server can handel this.

If you have to create a new instance or only a new schema to seperate the data depends
on the applications. (if one is OLTP and the other DSS = 2 instance or better 2 servers).
If it's a development server with x programmer, different schema would be right.

Hope this helps
eugen Received on Thu Apr 23 1998 - 07:19:32 CDT