Re: Newbie: Creating new database files

From: sPh <sphealeyxxx_at_xxxworldnet.att.net>
Date: Tue, 31 Oct 2006 13:53:19 GMT
Message-ID: <jzI1h.156458$QZ1.24836@bgtnsc04-news.ops.worldnet.att.net>

>Ade wrote:
> Ideally, as with Access previously, I would expect each application I write
> to have their own set of files which can be stored away from other
> applications. This was so easily done with Access (sorry if I'm swearing. by
> the way!!).
>
> With Oracle it appears that there is a central database area underneath the
> Oracle directory tree which will contain data for all applications using it.
> I can only see a separation between applications by the use of a
> username/password combination. Like I said, I'm a complete Newbie to Oracle,
> so please excuse me if I'm way off track.

True active RDBMS systems, including Oracle, SQL Server, DB2, and others, are vastly different from single-user file-based database such as Access. I suggest that the best place to start would be to download the Concepts Guide from the Oracle documentation set and read through it at least twice. The Concepts Guide is only 1% or less of the complete documentation set but it has more information about Oracle packed into it than any other source I have seen. Just about any answer to any question about Oracle that you receive from a knowledgeable source will start with "have you read the Concepts Guide for your version?", so might as well get started!

Briefly, Oracle has the concepts of database, instance, and schema. Schemas can roughly be thought of as userids to get started. Typically each application will store its data in a schema. Tables and fields are then referenced using either their name in context or their fully qualified name:

      PART.LENGTH <== if the context is known
      ERP.PART.LENGTH
      PDM.PART.LENGTH <== here we have two tables and fields
                          with the same name in two different
                          applications referenced with the fully
                          qualified names

There are other levels of abstraction for accessing multiple instances, multiple databases, remote databases, etc.

Steven Received on Tue Oct 31 2006 - 07:53:19 CST