Re: "Correct" term for a 1:1 relationship between a "database" and an "instance" where > 1 such things are on the same physical server?

From: John Hurley <>
Date: Wed, 22 Jul 2009 16:26:25 -0700 (PDT)
Message-ID: <>

On Jul 22, 8:24 am, dana <> wrote:
> What is the "correct" term for a 1:1 relationship between a "database"
> and an "instance" where there are at least two such "things" on the
> same physical server?
> Nearly all the Oracle docs and books define a database something like
> the following:
> DATABASE - a collection of datafiles and oracle config files; useless
> without an "instance" to access the database.
> INSTANCE - a collection of background procs and memory structures,
> used to access a "database."
> Where I work, people typically call each "thing" mentioned in my
> Subject: line an "instance" or a "database instance." What is the
> "correct" term for having more than one of these "things" on the same,
> unpartitioned physical server?
> This may be splitting hairs; but when people don't or can't come to
> terms, confusion ensues--and that's typically a Bad Thing.
> I noticed, or rather a colleague of mine did, that even Tom Kyte mixes
> terms. In the book Expert Oracle Database Architecture (2005 edition)
> on page 50, in the bullet-pointed definitional paragraph for Instance,
> he throws the word "database instance" into the mix. A "no no"
> according to my colleague (don't shoot the messenger, please); because
> the vernacular seems to be "instance" or "database instance" for the
> each "thing."
> I like to be precise with terms, but then there are business
> stakeholders who use technically imprecise terms; even DBAs seem to
> make this mistake.
> Would it be less confusing to all concerned simply refer to an "Oracle
> SID" to indicate a 1:1 pairing of an "instance" and a "database" where
> there are 2 or more of these "things" on a single, unpartitioned
> server?
> Help! I want to "get it right" without being pedantic and trying to
> educate every last stakeholder in a large organization. Maybe
> education is the "right" thing to do, but when even DBAs use the term
> "instance" incorrectly... well, that might not end well. :-)
> Dana

You cannot talk about something as complicated as Oracle and get things right technically without being verbose and wordy and extremely specific.

Most Oracle DBA ( well many anyhow ) understand the differences between instances and databases but tend to get sloppy at times when talking to management, developers, IT operators, etc.

Might be best to count things on a server by server bases ( any VM's on a server should count as a server ) and define how many instances each server supports in these categories: single instance oracle databases and multiple instance oracle databases. The multiple instance databases are typically RAC although there is still some OPS ( Oracle Parallel Server ) hanging around still. Received on Wed Jul 22 2009 - 18:26:25 CDT

Original text of this message