Re: definition of database

One instance always manage one database, with the exception of Oracle Parallel Server where two (or more) instance on different systems can manage one database. An instance is nothing more than a limited number of background processes overseeing the database.
It is indeed possible to have multiple database (and thus multiple instances). IMHO this should either be avoided or the system should be upgraded appriopately. Miminum instance probably will use about 20M of SGA (system global area, cache) not counting the background processes. I have seen several situations where those multiple instance were underutilized, ie several were doing nothing, except using up resoures.

Hth,

Sybrand Bakker, Oracle DBA

pburke_at_american.edu wrote:

> I had understood from reading here and from 3rd party books on Oracle that
> the term "database" is used interchangeably with "instance". However, after
> we installed one instance of Oracle and created the default database, I had
> access to the online Oracle documentation and read in the Oracle8
> Administrator's Guide (we installed Oracle 8 Enterprise Edition on a Unix Sun
> OS 5.6) that we "can use this initial database and customize it to meet your
> information management requirements, or discard it and create one or MORE new
> databases to replace it".
>
> Does this mean that I can create an additional database on the same instance?
> The potential advantage I see is a smaller unit of recovery (i.e., faster)
> if only one logically related group of datafiles needs to be recovered, since
> each database has its own control files, redo logs, System tablespace,
> dictionary, etc. It would appear that administration of multiple databases in
> one instance with the Oracle architecture might be more complex, however.
>
> I am a DBA from the DB2/MVS world, with some Sybase (yuck) experience, and the
> same terms have very different meanings, depending on the environment.
>
> Can MORE than one Oracle "database" be created in one instance? If not,
> is the Oracle8 Administrator's Guide paragraph above referring to creating
> MORE than one database on a *server*???? Thanks in advance. Please
> respond to mailto:pburke_at_ibm.net or mailto:pburke_at_american.edu, thanks.
>
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Received on Wed Nov 18 1998 - 14:50:24 CST