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 <johnbhurley@xxxxxxxxxxxxx>
- Date: Wed, 22 Jul 2009 16:26:25 -0700 (PDT)
On Jul 22, 8:24 am, dana <dana_at_w...@xxxxxxxxx> 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
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
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
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. :-)
You cannot talk about something as complicated as Oracle and get
things right technically without being verbose and wordy and extremely
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.
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