Re: newbie: multiple databases

Kim,

This is also easy to do in Oracle, you just need to get used to a different nomenclature.

As long as your operating system supports shared memory and multitasking, creating and operating multiple Oracle instances/databases on one host is pretty straightforward.

An Oracle instance consists of a System Global Area (SGA an area in shared memory) and several background processes. A Oracle database is the collection of physical files where the data actually reside. The system global area and the background processes of the instance provide user access to and control the operation of the physical database.

In order to create three different databases on one host, you will need to create init.ora files for each of three instances you will need to have running in order to control the three databases (e.g initFIRST.ora, initSECND.ora, initTHIRD.ora...FIRST, SECND, and THIRD being the ORACLE_SID (system identifier)for the respective instances.

Once you have created the appropriate initSID.ora files, you will need to use Server Manager to startup (nomount) the respective instances. You will then use the CREATE DATABASE command (preferably in a script) to create your baseline database.

Your Oracle installation should include sample init.ora files as well as database creation scripts and other scripts necessary to create a baseline database. These should be in the ORACLE_HOME/dbs directory. (ORACLE_HOME is the directory where you installed your Oracle software distribution).

The Oracle7 Server SQL Reference Manual, and Administrator's Guide both provide considerable information on database creation.

Hope this helps,

regards,
Chuck

Kim Wykoff wrote:
>
> Coming from a Sybase background, I find Oracle really hard to grasp.
>
> I'm trying to set up three different databases on one host. I want them
> all to be accessible and running at all times.
>
> In Sybase this would be very easy because there is just one database
> server in which I create the three databases. As long as the server
> were running, I would be able to access any database I wanted or all
> three simultaneously.
>
> With Oracle it seems that only one database can be running at any one
> time within one "server" or "instance". So does that mean that I must
> have 3 servers running? And how do I create these other servers? Do I
> have to install each server or is there an easy way to replicate the
> servers?
>
> I don't understand Oracle's concept of a database server even though
> I've been reading the dba handbook on the architecture. Maybe it's
> because I keep trying to relate it to Sybase and it doesn't fit.
>
> Help would be much appreciated. Thank you,
>
> kim
 

-- 
*************************************************************************
*   Chuck Wolfe                         
*   Oracle DBA
*   The Ryland Group
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*   cwolfe_at_ix.netcom.com
* 
*   All the usual discalimers apply, except where otherwise indicated...
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