Re: Oracle Instance vs Oracle Database

"Charles Davis" <Stratford2000_at_home.net> wrote in message news:3AA04B5F.A5AD09BF_at_home.net...
> I have a basic question about instances and databases.
>
> Does one Oracle Instance equate to only one Oracle database?
>

in Oracle, yes, one instance is one database. except in the case of parallel server, where two instances can share a single database.

> In other words, can I have separate databases running within one Oracle
> instance??

no. an oracle database is one set of files and data structures.

>
> I corelate this to having many separate MS SQL Server databases running
> within one SQL Server instance (service).
>

the meaning of "database" in Oracle differs from the meaning of the term in SQL Server. within an Oracle database, you create a user. a user can own objects (tables, views, procedures, etc.). all of the objects owned by a user
make up what is called a "schema". each "schema" is separate and distinct from one another. that is, two or more users can own an object with the same
name. that is, the table EMP owned by SCOTT is a different object than the table EMP owned by GEORGE. in order for a user to access an object in another user's schema, appropriate privileges must be granted (usually by the owner of the object), and the name of the object must be qualified with the
username of the owner... e.g. SELECT * FROM SCOTT.EMP

> I am a new Oracle DBA working with Oracle NT and Oracle Unix and my
> question applies to both.

The Oracle model of instance, database, user, schema, object, privilege, and so on remains constant across the platforms.

> Can someone clarify this for me? Many thanks.

I'd suggest you start with the Oracle concepts manual... and do NOT assume that Oracle terminology is the same as that used for Sybase/SQLServer.

> Charlie
Received on Fri Mar 02 2001 - 21:57:33 CST