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Re: What is a Catalog and Database according to Oracle?

From: Joseph Weinstein <joe_at_weblogic.com>
Date: Mon, 20 Sep 1999 14:13:23 -0700
Message-ID: <37E6A373.B7EBF6B@weblogic.com>

Hi. A catalog can be viewed most precisely as a complete standalone collection of system tables. These define all the users, tables indices etc for a database. An Oracle instance is a single catalog, and you cannot have multiple catalogs within an Oracle instance. Some DBMSes, like Sybase and MS SQLServer can and do have multiple catalogs withing a single instance, so while connected to a given Sybase instance you can change your database context to different daatabases, each of which have an independent and complete list of tables, users etc.

   A 'user' corresponds to the term 'Schema'.

Steven Hill wrote:

> I'm trying to reconcile some Oracle terms with some ANSI SQL & JDBC
> terminology and I'd like to know if I've made any mistakes. In other
> word, which of the following statements are false and why?
>
> 1) An "Oracle database" is an instance of an Oracle DBMS, thus if there
> is more than one instance running on a computer then the computer has
> more than one database running?
>
> 2) Do Oracle DBAs use the terms "Oracle database" and "Oracle server"
> interchangably? Or does "server" mean one computer with possibly
> multiple databases running on it.
>
> 3) Is an "Oracle user" the same as the ANSI SQL term "catalog"? If so,
> then a Oracle user can have only one catalog? Do Oracle DBA's call a
> catalog the "user's database"?
>
> 4) The Oracle docs say that a user account can only own a single schema
> which has the same name as the user name.
> Therefore, a user's catalog or user's database (identified by the user's
> name) contains one schema owned by the user (also identified by the
> user's name) and portions of other users' catalogs/schemas which the
> user has access to?
>
> 5) An Oracle DBA can setup up additional user accounts, say 5, for the
> same user ie, JSmith1, JSmith2... JSmith5. with different schema access
> privileges; thus, simulating one ANSI SQL "cluster", defined as a
> "group of catalogs" and not to be confused with Oracle cluster meaning?
>
> 6) The scope of an "Oracle user" OWNERSHIP is limited to one database
> -- the one it is defined on?
>
> 7) The scope of an "Oracle user" ACCESS can span multiple databases
> using dblinks? Therefore, a user's catalog can span multiple databases?
>
> 8) "Oracle dblinks" allow remote objects in a different "Oracle
> database" to be seemlessly included in a user's catalog? So, for
> example, issuing one Oracle request for a list of all tables that a user
> has access to will include any remote tables distinguished by datalink @
> tablename syntax. ?
>
> 9) Or is the same request also needed on remote database inorder to
> discover the remote tables? If this true, how does the client app know
> what datalink to use if it is not hard-coded in the app?
>
> TIA,
> --
> Steven Hill

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Received on Mon Sep 20 1999 - 16:13:23 CDT

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